BoletÃÂn Informativo Del Sistema Interamericano De MetrologÃÂa Oea
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osto 2009 / Aug F
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BOLETÍN INFORMATIVO DEL
SISTEMA INTERAMERICANO
DE METROLOGÍA - OEA
INFORMATIVE BULLETIN OF
THE INTERAMERICAN METROLOGY
SYSTEM - OAS
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SISTEMA
INTERAMERICANO
DE METROLOGÍA
DIRECTORIO
DIRECTORY
Presidente
President
Humberto S. Brandi, INMETRO, Brazil
Secretario Ejecutivo
Executive Secretary
Oscar Harasic, OEA / OAS
Consejero Técnico
Technical Advisor
Claire Saundry, NIST, USA
Coordinador del Comité Técnico
Technical Committee Chair
Alan Steele, INMS-NRC, Canada
Coordinador del Comité de Desarrollo Profesional
Professional Development Committee Chair
Ignacio Hernandez, CENAM, México
Coordinador del Grupo de Trabajo sobre Sistemas
de Calidad
Quality Systems Task Force Chair
William Anderson, NIST, USA
Secretario
Secretary
Jorge A. Paz Cruz, INMETRO, Brazil
COORDINADORES DE LAS SUBREGIONES
SUBREGION COORDINATORS
ANDIMET
Juan Carlos Castillo Villarroel, IBMETRO, Bolivia
CAMET
Gustavo Montiel Quedo, LANAMET, Nicaragua
CARIMET
Theodore Reddock, TTBS, Trinidad and Tobago
NORAMET
Jim McLaren, NRC, Canada
INFO IM
SURAMET
Ever Cabrera, INTN, Paraguay
www.sim-metrologia.org.br/
INFOSIM
ÍNDICE / CONTENTS
INTRODUCCIÓN / INTRODUCTION ……………………………….......................................... 5
Humberto Brandi
METROLOGÍA, INNOVACIÓN Y COMPETITIVIDAD …............................................................ 7
Oscar Harasic
ENSAYO DE APTITUD REALIZADO EN LATU PARA VALIDAR EL MÉTODO DE
CALIBRACIÓN Y USO DE PIPETAS DE VIDRIO Y PIPETAS AUTOMÁTICAS…………………..... 9
Claudia Santo, Pablo Constantino, Andrea Sica
DIMENSIONAL CALIBRATION TECHNIQUES FOR PRESSURE BALANCES TO BE USED
IN THE NEW DETERMINATION OF THE BOLTZMANN CONSTANT............................................. 14
Otto Jusko, Michael Neugebauer, Helge Reimann, Wladimir Sabuga, Tasanee Priruenrom
ENABLING STANDARDS FOR NANOMATERIAL CHARACTERIZATION……………….……….… 24
Vincent A. Hackley, Martin Fritts, James F. Kelly, Anil K. Patri, Alan F. Rawle
HARDNESS MEASUREMENT IN BRAZIL IN THE NANOTECHNOLOGY ERA.............................. 30
Renato Reis Machado, Geralda Cristina Durães de Godoy, Margareth Spangler Andrade
THE NANOSCALE: THE SMALLEST NEW BIG DEAL IN MEASUREMENT AT NRC…...………... 37
Co-written by National Research Council Canada scientists and writers
ESTABLISHMENT OF THE SIM TIME SCALE……………………………………......…….……........ 39
J. M. López-Romero, N. Díaz-Muñoz, M. A. Lombardi
CRONOSIM: BREVE RESEÑA DE LOS ORÍGENES DEL SIM.......……………………….…….…
44
Anselmo Manuel Araolaza - Rodríguez
NOTISIM ..………………………………………………………………………….…………...……........
47
SOBRE LA POSIBLE REDEFINICIÓN DEL KILOGRAMO ……………….…………...……........
49
Luis Omar Becerra Santiago
INTRODUCCIÓN
INTRODUCTION
Es imprescindible para el desarrollo de una economía
It is essential for the development of the economies to
asegurar la uniformidad de las medidas y vincular el
ensure the uniformity of the measurements and to link the
conocimiento científico y el progreso tecnológico con
scientific knowledge and the technological progress with
aplicaciones que aseguren la consistencia de las
applications aimed to assure the consistency of the
mediciones. Contribuye a ello, el conocimiento de las
measurements. The knowledge of innovations which are
innovaciones que se hacen en estos campos, y su
realized in this fields and its dissemination contribute to it.
divulgación.
Therefore the INFOSIM plays an important role as a
Por eso es importante el INFOSIM como medio de
means of diffusion toward the community of the Inter-
difusión para la comunidad del Sistema Interamericano
American Metrology System (SIM).
de Metrología.
This edition reproduces contributions about the
En este número se reproducen aportaciones sobre el
proficiency test to validate the calibration method of
ensayo de aptitud para validar el método de calibración
pipettes as a medium to demonstrate the technical
de pipetas como un medio para demostrar la capacidad
capability of the test laboratory analysts and to unify its
técnica de los analistas de laboratorios de ensayo y para
criteria within calibration methods, as well as about the
unificar sus criterios en torno a los métodos de
techniques for the dimensional calibration of pressure
calibración, así como sobre las técnicas para la
balances to be used in the new determination of the
calibración dimensional de balanzas de presión usadas
Boltzmann constant. In the nanotechnology field we
en la nueva determinación de la constante de Boltzmann.
count with three contributions: one on the standards for
En el campo de la nanotecnología, tenemos tres
the characterization of the physical-chemical and
contribuciones: uno referente a patrones para la
biological properties of the nanomaterials, the other
caracterización de las propiedades físico-químicas y
biológicas de los nanomateriales, otra referente a la
about the measurement of hardness in Brazil in the era of
medición de dureza en el Brasil en la era de la
nanotechnology and finally the nanoscale in the NRC.
nanotecnología y por último, la nanoescala en el NRC. El
The establishment of the SIM time scale is another
establecimiento de la escala de tiempo del SIM, es otra
interesting contribution which appears in this edition.
In addition to the section NOTSIM in which the relevant
interesante contribución que aparece en esta edición.
Además de la columna NOTISIM en la que damos a
events of our community are presented, this edition also
conocer los acontecimientos relevantes de nuestra
started the section CRONOSIM, to guides us throughout
comunidad, en este número hemos iniciado la sección,
time and space to remind, to those who experimented it,
CRONOSIM, que nos llevará por el tiempo y el espacio a
and to present to those who did not, the origin of the SIM,
recordar, para los que lo vivimos y a conocer para los que
through the testimony of its protagonists.
no, el orígen de nuestro SIM, con el testimonio de
aquellos que fueron protagonistas de este
Humberto Brandi,
President of the SIM
acontecimiento.
Humberto Brandi,
Presidente del SIM
5
4
6
CONTRIBUCIÓN ESPECIAL
SPECIAL CONTRIBUTION
METROLOGÍA, INNOVACIÓN Y COMPETITIVIDAD
Oscar Harasic
Organización de los Estados Americanos
A través de la historia no ha habido desarrollo
Throughout history, no technological development
tecnológico que se haya logrado sin una base de
has been achieved without the support of a
mediciones confiable. A su vez, la metrología,
reliable measurement basis. Besides, Metrology,
que es la ciencia de las mediciones, cuenta con
the science of measurements, uses more
instrumentos cada vez más sofisticados que son
sophisticated instruments every time obtained
p r o d u c t o d e c o n s t a n t e s i n n o v a c i o n e s
from technological innovations generally
tecnológicas, generalmente provenientes de los
originated in economies with high levels of
países con alto grado de desarrollo.
development.
La medición de longitud ilustra claramente el
The measurement of length clearly illustrates the
proceso de innovación a partir de tecnologías
innovation process starting from available
disponibles y que, con el paso del tiempo, han
technologies that, throughout the time, have
permitido mediciones más exactas. A partir de su
allowed more accurate measurements. From its
definición, el metro ha pasado de un patrón físico
definition, the meter has been realized, first, by a
(barra de platino-iridio), a la longitud de onda de
physical standard in the form of a platinum-iridium
una radiación emitida por el isótopo 86 del krypton
bar, then by the wavelength of a radiation emitted
y recientemente a la medición basada en la
by the isotope 86 of krypton, and nowadays the
velocidad de la luz utilizando un láser estabilizado.
definition is based on the speed of light by using a
El láser fue el resultado de un proceso de
stabilized laser.
investigación y desarrollo sin aplicaciones
previstas cuando fue inventado. Sin embargo, hoy
The laser became the result of a research and
en día, tiene múltiples aplicaciones no solo en la
development process without any foreseen
metrología sino en varias ramas de la medicina, la
applications at the time of its invention. However,
astronomía y la exploración espacial, solo por
today it has multiple applications in the astronomy
mencionar algunos ejemplos.
and in space exploring, as examples, besides
those in metrology.
En efecto, la innovación es la aplicación de una
idea hasta su explotación efectiva en beneficio
As a matter of fact, innovation means to pursue an
directo para la sociedad. Su relevancia ha sido
idea until its effective exploitation to directly
destacada en la reciente Segunda Reunión de
benefit the society. Its relevance has been
Ministros y Altas Autoridades en Ciencia y
highlighted in the Second Meeting of Ministers and
Tecnología promovida por la OEA, llevada a cabo
High Authorities on Science and Technology held
en octubre de 2008 en la Cd. de México, cuyo
in Mexico in October 2008, promoted by the OAS,
tema central fue "Ciencia, tecnología, ingeniería e
where the "Science, technology, engineering and
innovación para la prosperidad", y la cual produjo
innovation for prosperity" was its central theme,
una nota de atención a las autoridades para
and produced a call to the authorities for
esforzarse en incrementar la inversión pública y
"endeavoring to increase public and private
privada en ciencia, tecnología, ingeniería e
investment in science, technology, engineering
innovación. Para lograrlo, evidentemente debe
and innovation". In order to achieve it,
considerarse que la medición constituye uno de
measurements should be considered as one of
los pilares indispensables.
the indispensable pillars.
7
Mientras que en el pasado, los recursos naturales
While the natural resources and raw materials
y materias primas eran los elementos principales
were the main elements for trade and wealth in the
del comercio y la riqueza, hoy en día la mayor parte
past, nowadays most of the worlds commerce
del comercio mundial está compuesta por
deals with manufactured products, with
productos manufacturados y dentro de ellos
predominance of those of high technological
predominan aquellos con alto contenido
content. The highly developed countries host
tecnológico. Los países con mayor desarrollo
organizations that have been able to innovate their
tecnológico han atraído empresas que han sabido
processes and products, and so have reached a
innovar sus procesos y productos, y en
major share in the world trade, impacting the
c o n s e c u e n c i a h a n l o g r a d o u n a m a y o r
quality of life of their people. These countries
participación en el comercio mundial, lo cual ha
count on an excellent national structure for quality
redundado en una mejor calidad de vida para sus
as a result of several decades of fostering and
habitantes. Estos países cuentan con una
support to their measurement systems. Such an
excelente infraestructura nacional de calidad
infrastructure should be based on five main
resultado de varias décadas de fomento y apoyo a
components: metrology, standardization, testing,
sus sistemas de mediciones. Dicha infraestructura
accreditation and certification, being metrology
debe apoyarse en cinco componentes principales:
the basis for this structure to operate. Therefore, a
metrología, normalización, pruebas y ensayos,
national quality infrastructure is fundamental to
acreditación y certificación, siendo la metrología la
promote innovation, productivity and international
base para que funcione dicha infraestructura. Por
competitiveness.
ello, una infraestructura nacional de calidad es
fundamental para impulsar la innovación, la
The search for improving quality starts with
productividad y la comptetitividad internacional.
measurements to reach products and processes
certification, by a quality seal to guarantee the
La búsqueda del mejoramiento de calidad se inicia
stated specifications by the supplier or the
con mediciones para llegar a la certificación de
customer requirements as one of the ways.
productos y procesos y puede tomar la forma de un
Quality certification together with the prices of
sello de calidad que garantiza las especificaciones
products and services, and the way these are
declaradas por el productor o los requerimientos
supplied are warrants of the competitiveness in
del consumidor. La certificación de la calidad junto
the national as well as international markets. By
con el precio de los productos y servicios, y las
means of the competitiveness, the organizations
formas en que éstos son proporcionados garantiza
obtain access to new markets and keep their
la competitividad en los mercados nacionales e
already established ones. This expansion helps to
internacionales. Por medio de la competitividad
create new jobs and greater income, that
las empresas obtienen acceso a nuevos mercados
contribute to raise the quality standards, to
y mantienen sus mercados ya establecidos. Esta
eradicate poverty and to a better technological,
expansión ayuda a crear nuevos empleos y
e c o n o m i c a l a n d s o c i a l d e v e l o p m e n t .
mayores ingresos económicos, que a su vez
Measurement systems in the organizations are
contribuyen a elevar la calidad de vida, ayudan a
essential elements to support innovation
erradicar la pobreza y a un mayor desarrollo
processes to help the raise in productivity and
tecnológico, económico y social. Los sistemas de
competitiveness.
medición en las empresas son esenciales para
apoyar procesos de innovación que ayuden a
elevar su productividad y competitividad.
8
ENSAYO DE APTITUD REALIZADO EN LATU PARA VALIDAR EL MÉTODO
DE CALIBRACIÓN Y USO DE PIPETAS DE VIDRIO Y PIPETAS
AUTOMÁTICAS
Claudia Santo, Pablo Constantino, Andrea Sica
Laboratorio Tecnológico del Uruguay
Av. Italia 6201, 11500, Montevideo, Uruguay.
csanto@latu.org.uy
RESUMEN
Se realizó en 2008 un ensayo de aptitud con la participación de varios analistas (nuevos en su mayoría) de los laboratorios de
ensayo del LATU. Para la misma se utilizaron dos pipetas, una de vidrio de 1 ml, clase A y una pipeta automática de volumen
regulable entre 0 y 1 ml, la cual se calibró para el valor correspondiente a 1 ml, Se pidió que cada analista repitiera entre 6 y 10
veces cada pipeta, con el fin de evaluar la repetibilidad en la medición. Se evaluó la media de cada analista para cada pipeta y
se estimó la incertidumbre expandida del valor medio obtenido por cada analista. Se presentan los gráficos con las medias y
las incertidumbres obtenidas para cada tipo de pipeta. Se realiza un estudio comparativo de los mismos. Como conclusión se
evalúa la reproducibilidad de cada tipo de instrumento, en base a lo cual se realizan recomendaciones para su uso y
calibración.
1. INTRODUCCIÓN
Ensayos de Aptitud en calibración de material
volumétrico periódicos en el que participan los nuevos
El LATU es una institución certificada por la norma ISO
analistas (de forma de validar la forma de uso del
9001 [1] y aproximadamente 250 ensayos químicos y
material volumétrico) y analistas más experimentados
físicos se encuentran acreditados por la norma ISO
(para evaluar si sus resultados siguen estando en
17025 [2]. Está implementado por lo tanto un Sistema
tolerancia).
de Gestión que asegura la calidad de los resultados
emitidos. En el punto 7.6 de la ISO 9001, así como en el
Debemos tener en consideración que los problemas
punto 5.6 de la ISO 17025 se establece la necesidad de
detectados en la calibración del material volumétrico,
utilizar equipamiento calibrado durante la realización de
reflejan problemas en el uso del mismo, o sea en todos
los ensayos.
los procesos que involucren material volumétrico.
Como estamos hablando de una institución grande, que
Frente a la gran cantidad de métodos químicos
incluye diferentes Departamentos analíticos
existentes que involucran, a su vez, un número creciente
especializados, la cantidad de material volumétrico que
de matrices y analitos, nos enfrentamos, desde el punto
se utiliza en los mismos es muy grande. En el pasado
de vista metrológico, ante la falta de oferta de
todo el material volumétrico era calibrado en al área de
interlaboratorios y/o de materiales de referencia para
volumen correspondiente al Departamento de
cada método y en cada analito y matriz. Es en estos
Metrología. Para mejorar la gestión de los recursos y la
casos que se debe recurrir a la evaluación de los
calidad de los resultados analíticos se implementó la
métodos químicos, asegurando metrológicamente cada
política de calibrar el material volumétrico por parte del
subproceso involucrado (por ejemplo: uso de material
personal de cada uno de los departamentos que hace
volumétrico, extracciones, separación cromatográfica,
uso del mismo. Esto tiene la ventaja de asegurar que el
etc.). Teniendo esto en cuenta es importante tener el
material se calibre en las mismas condiciones y con la
subproceso de uso de material volumétrico en control.
misma metodología con que se usa, disminuyendo de
esta forma los errores sistemáticos en el uso y
En cada Ensayo de Aptitud, se selecciona un par de
favoreciendo el entrenamiento del personal que utiliza
ítems de material volumétrico que son calibrados por
el material volumétrico, haciéndolo participar del
técnicos del Departamento de Metrología para
proceso de calibración.
asignarles el valor de referencia. El método utilizado
Para evaluar la competencia del personal, la calibración
está plasmado en un procedimiento interno de
del equipamiento y el aseguramiento de calidad en los
calibración basado en las normas ISO 4787 [3] e ISO
distintos Departamentos, se han implementado
648 [4] por ejemplo en el caso de pipetas. Luego los
1 This paper is reproduced from the Proceedings of the Simposio de Metrologia 2008, CENAM, México, with permission of its authors and the
Simposio's organizers.
9
mismos se hacen circular según un plan especificado
2. PARTICIPANTES
entre los analistas de los distintos Departamentos
analíticos del LATU para que procedan a su calibración
Participaron 10 analistas de distintos departamentos
utilizando el mismo procedimiento. Luego de realizada
del LATU, 8 de ellos pertenecientes al área química y
la misma, los resultados de calibración acompañados
los 2 restantes al área de volumen del Departamento de
de sus respectivas incertidumbres son informados al
Metrología.
organizador, quien procesa los datos, evalúa los
mismos y confecciona un reporte. Luego se realiza una
El valor de referencia fue calculado como el promedio
reunión de devolución con los participantes donde se
ponderado de los valores obtenidos por los técnicos del
discuten los resultados, se asignan causas probables a
área de volumen del Departamento de Metrología en el
las tendencias y desviaciones y se evalúan posibles
caso de la pipeta aforada y por la media aritmética de
acciones correctivas y preventivas a implementar.
los participantes en el caso de la pipeta automática. Las
mediciones de volumen son trazables al Sistema
En el caso del ensayo de aptitud objeto del presente
Internacional, ya que se tiene un sistema de calidad
estudio se evaluó la competencia de distintos analistas
basado en la ISO 17025, y las capacidades de masa y
en el uso y calibración de una pipeta aforada de vidrio
temperatura están declaradas en el apéndice C del
de 1 ml (la cual fue seleccionada de forma de que los
acuerdo de reconocimiento mutuo del CIPM. Además
errores de manipulación se vieran amplificados por su
se ha participado en Intercomparaciones en volumen
forma de construcción y descarga) y una pipeta
en el marco del SIM en forma exitosa.
automática de volumen variable en la cual se
seleccionó un volumen de 1 ml.
3. RESULTADOS
Los resultados obtenidos sirvieron no solo para evaluar
la calidad de las mediciones de volumen en los
3.1. Resultados Pipeta de Vidrio
Departamentos, sino también para comparar el
comportamiento en el uso de estos dos tipos de pipetas
y las fuentes de incertidumbre asociadas a cada una y
su cuantificación.
Tabla 1. Resultados obtenidos para la pipeta aforada.
Analista
1
2
3
4
5
6
7
8
9
10
Resultado
0,9612
0,9655
0,9696
0,9983
0,9677
0,9925
0,9995
0,9708
0,9800
0,9926
Laboratorio/
cm3
Incertidumbre
0,0077
0,0018
0,0044
0,0054
0,0073
0,0079
0,0029
0,0012
0,021
0,0084
Analista/cm3
Valor de
0,9653
0,9653
0,9653
0,9653
0,9653
0,9653
0,9653
0,9653
0,9653
0,9653
referencia/cm3
Incertidumbre
0,0150
0,0150
0,0150
0,0150
0,0150
0,0150
0,0150
0,0150
0,0150
0,0150
V alor
Referencia/cm3
Error /cm3
-0,0041 0,0002
0,0044
0,0330
0,0024
0,0272
0,0342
0,0055
0,0147
0,0273
Error relativo
-0,0041 0,0002
0,0044
0,0330
0,0024
0,0272
0,0342
0,0055
0,0147
0,0273
Error
-0,24
0,01
0,28
2,07
0,14
1,61
2,24
0,37
0,57
1,59
normalizado
PIPETA AFORADA
1,01
1
3 0,99
m
/
c
n
e 0,98
m
Datos- analistas
l
u
o 0,97
Referencia
V
tolerancia clase B
0,96
0,95
0
2
4
6
8
10
12
Identificación - Analista
Fig.1. Gráfico de resultados con su incertidumbre- pipeta aforada.
10
3.2. Resultados de Pipeta Automática
Ta b l a 2 . R e s u l t a d o s o b t e n i d o s p a r a l a p i p e t a a u t o m á t i c a
Laboratorio
1
2
3
4
5
6
7
8
9
10
Resultado
1,0035
1,0056
0,993
1,0004
1
0,9993
0,9986
1,0028
0,9995
1,0053
Laboratorio/
3
cm3
Incertidumbre
0,0008
0,0008
0,004
0,0044
0,0002
0,0007
0,0015
0,0008
0,0013
0,0032
9
Laboratorio/cm3
Valor de
1,00083 1,00083 1,000
1,00083
1,00083 1,00083 1,00083 1,00083 1,00083 1,00083
referencia/cm3
83
Incertidumbre
0,005
0,005
0,005
0,005
0,005
0,005
0,005
0,005
0,005
0,005
Valor
Referencia/cm3
Error /cm3
0,0027
0,0048
-
-0,0004
-0,0008
-0,0015
-0,0022
0,0020
-0,0013
0,0045
0,007
5
Error relativo
0,0027
0,0048
-
-0,0004
-0,0008
-0,0015
-0,0022
0,0020
-0,0013
0,0045
0,007
5
Error
0,53
0,94
-1,08
-0,06
-0,17
-
0,30
-0,43
0,39
-
0,26
0,75
normalizado
PIPETA AUTOMÁTICA
1,01
1,005
3
m
1
/
c
n
e
Datos- analistas
m
Referencia
l
u 0,995
o
Tolerancia 0,5 %
V
Tolerancia 0,5 %
0,99
0,985
0
2
4
6
8
10
12
Identificación- Analista
Fig. 2. Gráfico de resultados con su incertidumbre- pipeta automática.
11
3.3. Resultados de Repetibilidad de las dos Pipetas
Tabla 3. Desvíos estándar de los valores obtenidos para cada pipeta.
ANALISTA
1
2
3
4
5
6
7
8
9
10
PIPETA DE
VIDRIO/ml
0,0108 0,0
024 0,013 0 0,0024 0,0065 0,0
110 0,0027 0,0019 0,0
182 0,0030
PIPETA
AUTOMÁTICA/ml
0,0007 0,0009 0,0059 0,0050 0,0027 0,0009 0,0019 0,0009 0,0017 0,0017
Repetibilidad
0,0200
0,0180
3
0,0160
m
r
/
c
0,0140
a
d
Pipeta de vidrio
n
0,0120
t
á
Media Pipeta vidrio
s
0,0100
E
Pipeta Automática
n
0,0080
i
ó
c
Media Pipeta Automática
i
a
0,0060
v
s
e
0,0040
D
0,0020
0,0000
0
2
4
6
8
10
12
Identificación - Analista
Fig. 3. Gráfico de desvíos estándar
NOTAS:
Para ver la significancia real en un posible
E
E =
resultado, por ejemplo de una solución valorada,
A)
n
(
U 2
2
si se sigue el mismo procedimiento que el utilizado
LATU
U LAB )
+
en la calibración se ve en la fila de “errores
E
relativos”. Por ejemplo el valor final de una
n
- Error normalizado
solución valorada preparada por cada analista
E
- Error = Valor informado por el analista –
participante tendrá un error relativo mayor o igual
Valor de referencia
que el que aparece en esta fila de la tabla.
U LATU - Incertidumbre en el valor de referencia
En el caso de la pipeta aforada se tomó
4. DISCUSIÓN
igual a la tolerancia de la misma y en
caso de la automática a un 0,5 % de su
En el caso de la pipeta aforada, 4 de los 10
volumen.
analistas presentan errores normalizados
mayores que 1.
U LAB - Incertidumbre en el valor informado por
el analista.
En el caso de la pipeta automática todos los
errores normalizados son inferiores a 1.
Un error normalizado superior a 1 implica que el
Inferimos que la pipeta automática tiene mejor
error en la medición es significativo.
reproducibilidad
Es una medida del número de incertidumbres
Podemos ver además que en el caso de las
(valores que surgen de combinar la incertidumbre
pipetas automáticas los valores de repetibilidad
en el valor de referencia con la informada por cada
son mejores
analista) que estamos alejados del valor de
referencia.
12
5. CONCLUSIONES
mejores de plaza y comparar el desempeño de
ambas con cada analista.
A los efectos de analizar los resultados obtenidos
y tomar las acciones correctivas necesarias, en
En el caso de la pipeta automática, los valores
caso de resultados no conformes para el uso
obtenidos tienen una mayor reproducibilidad, lo
propuesto, es importante tener en cuenta que
que evidencia que el método de descarga es el
algunas de las posibles causas de errores
mismo en todas las ocasiones y no parece
sistemáticos pueden ser:
depender apreciablemente de la fuerza y la forma
en que cada analista realiza la descarga.
·
En el caso de la pipeta aforada:
- Errores en el enrase
Teniendo esto en cuenta y observando los valores
- Diferencias en la forma de vaciado de la
de repetibilidad en la Fig. 3 se evidencia que la
misma respecto a la especificada en el
repetibilidad y reproducibilidad de las mediciones
procedimiento, sobre todo en la descarga final,
de volumen en el caso de la pipeta automática son
ya que se debe dejar el tiempo de escurrido
mejores que en el caso de la pipeta aforada de
especificado y no realizar ningún movimiento
vidrio.
brusco con la misma que provoque la descarga
de las últimas gotas que no caen por gravedad
Este ejercicio nos hace llegar a las siguientes
·
Con estos errores considerados en la mayoría
conclusiones:
de los casos se obtendrían valores superiores
a los que se obtienen si se sigue el
·
Cuando se usa material volumétrico aforado,
procedimiento en todos sus términos
sobre todo cuando sus volúmenes son
·
En el caso de la pipeta automática:
pequeños, debe procederse a una apropiada
- Diferencias en la forma y la fuerza utilizadas
selección del mismo
para presionar el mecanismo de vaciado de la
·
Debe mantenerse un entrenamiento continuo
misma
del personal en el uso adecuado del material
·
En ambas pipetas:
volumétrico
- Errores en las mediciones de temperatura
·
Es recomendable, en el caso de querer
- Errores originados por la calidad del agua
minimizar las incertidumbres, que la persona
destilada utilizada.
que usa el material volumétrico sea la misma
que lo calibra. Vemos en ambos tipos de
Se observa que en el caso de la pipeta aforada,
pipetas que los valores de repetibilidad son
hubo problemas de manipulación por parte de
mucho mejores que los de reproducibilidad, lo
a l g u n o s a n a l i s t a s , q u e h a c e n q u e l a
que nos hace concluir que si es la misma
reproducibilidad de los resultados no sea buena.
persona que usa y calibra, se obtendrán
Se eligió una pipeta de 1 ml clase B, de formato tal
menores incertidumbres en los resultados
que los posibles errores de manipulación se
·
El uso de pipetas automáticas disminuye la
vieran amplificados, de forma de evidenciar y
influencia del analista en los volúmenes
corregir los mismos. Esta evaluación se realizó en
entregados, siempre y cuando estas sean de
la reunión de discusión de resultados, donde se
buena calidad.
discutieron las posibles causas de los errores
c o n s t a t a d o s , p l a n t e á n d o s e t o d a s l a s
REFERENCIAS
posibilidades evaluadas. Se detectó que los
valores que están por encima, en su mayor parte
[1] ISO/IEC 17025:2005 General requirements for
se deben a que se realizó algún movimiento
the competence of testing and calibration
brusco de la pipeta, el cual provocó la salida de la
laboratories (2005) International Organization
última porción de agua de su interior que en otras
for Standardization, Geneva, Switzerland.
condiciones no se hubiera dado. Pueden haber
[2] ISO 9001 Quality management systems –
existido problemas también en la visualización del
R e q u i r e m e n t s ( 2 0 0 0 ) I n t e r n a t i o n a l
menisco. Se resolvió entonces proceder a un
Organization for Standardization, Geneva,
entrenamiento exhaustivo del personal para
Switzerland.
unificar los criterios de uso, sobre todo en el caso
[3] ISO 4787 Laboratory glassware volumetric
de bajos volúmenes, ya que en los ensayos de
glassware Methods for use and testing of
aptitud anteriores, con volúmenes mayores, los
capacity (1984) International Organization for
resultados han sido buenos. Como en este caso
Standardization, Geneva, Switzerland.
se usó una pipeta que amplificaba los problemas,
[4] ISO 648 Laboratory glassware One-mark
convendría repetir el estudio una vez finalizado el
pipettes (1977) International Organization for
entrenamiento además con una pipeta de las
Standardization, Geneva, Switzerland.
13
DIMENSIONAL CALIBRATION TECHNIQUES FOR PRESSURE BALANCES
TO BE USED IN THE NEW DETERMINATION OF THE BOLTZMANN
CONSTANT
.
1
1
1
1
2
Otto Jusko , Michael Neugebauer , Helge Reimann , Wladimir Sabuga , Tasanee Priruenrom
1Physikalisch-Technische Bundesanstalt, Braunschweig, Germany, Otto.Jusko@ptb.de
2National Institute of Metrology (Thailand) (NIMT), 3/4-5 Moo 3, Klong 5, Klong Luang, Pathumthani 12120, Thailand,
currently researcher at PTB, tasanee.priruenrom@ptb.de
Abstract
A measurement procedure for the dimensional calibration of piston-cylinder type primary pressure standards is described.
The piston-cylinder assemblies are intended to be used in a project for the re-determination of the Boltzmann constant. The
measurement procedure includes optical and mechanical contacting, form and diameter measurement. A numerical post-
processing procedure is applied to generate precise three-dimensional data sets of the piston-cylinder surfaces required for
the effective area determination.
Key words: pressure metrology, Boltzmann constant, dimensional metrology
1. INTRODUCTION
2.1 Piston-cylinder assemblies for the Boltzmann
Primary gas pressure standards up to 2 MPa are
project
frequently realized by pressure balances with piston-
To achieve the goal, special prototype piston-
cylinder assemblies as major measuring components.
2
2
cylinder assemblies of 20 cm and 2 cm nominal
The nominal effective area of such piston-cylinder
effective area have been designed and manufactured
2
2
assemblies varies typically between 5 cm and 20 cm .
by DH Instruments (USA). The assemblies are made
Their corresponding diameters range from 25 mm to 50
from tungsten-carbide. The effective area of the three 2
mm.
2
cm piston-cylinders will be linked to that of the three 20
The effective area of pressure balances is usually
2
cm assemblies and, as they are operated in the same
calculated by using Dadson's theory [1]. The calculation
2
pressure balances, the 2 cm assemblies will cover the
is based upon dimensional input data.
pressure range up to 7.5 MPa. The pressure distortion
This paper describes the needed measurement
coefficients of the piston-cylinder assemblies of both
procedures and the principle of the data analysis with
sizes will be determined from the elastic properties of
emphasis on the project for the re-determination of the
tungsten carbide, which the assemblies are made of,
Boltzmann constant.
and their dimensional properties applying FEM (Finite
Element Method) [4]. The consistency of the
2. THE RE-DETERMINATION OF THE BOLTZMANN
dimensionally based effective areas of the six piston-
CONSTANT
cylinder assemblies will be verified by cross-float
experiments.
PTB and other NMIs have started a project towards
a re-determination of the Boltzmann constant k . The
B
Boltzmann constant is the proportional factor between
thermal and mechanical energy. Therefore, the project
may lead to a new definition of the Kelvin [2]. The
chosen experimental method of the Boltzmann project
is the dielectric constant gas thermometry (DCGT). The
uncertainty of that method strongly depends on the
uncertainty of the absolute pressure to be measured in
the range up to 7 MPa (requirement: 1 part per million
(ppm) [3]. Consequently the pressure measurement
uncertainty for the Boltzmann constant project is very
demanding, resulting also in high demands for the
dimensional calibration utilised for the calculation of the
effective areas. The target for the standard uncertainty
of the radial values of the 3D data net of the piston-
cylinder calibration, including form and size, is
Fig 1. Piston (left) and cylinder (right) of a pressure standard
approximately 25 nm.
piston-cylinder assembly. This model was custom-made for
the Boltzmann constant project. The artefacts are mounted on
clamping disks.
1 This paper is reproduced from the Proceedings of the 1o. CONGRESSO INTERNACIOANAL DE METROLOGIA MECÁNICA, October 8-10,
2008, Rio de Janeiro, Brazil, with permission of its authors and of the Congress organizers.
14
3. MEASUREMENT EQUIPMENT
3.3 Diameter measurement instruments
3.1 Coordinate measurement machines
The MFU8 can also be used for diameter
In principle, the 3D calibration of piston-cylinder
measurements in the U > 50 nm uncertainty range,
pressure standards is a typical measurement task for
because PTB's version was extended by a plane-mirror
3D coordinate measuring machines (CMM). However,
interferometer.
the measurement uncertainty of CMMs generally is
Diameter measurements with the lowest achievable
larger than approx. 0.5 µm, in many cases larger than
uncertainty can be performed with PTB's reference
1 µm. These values are more than a decade too high.
length comparator KOMF [8]. That instrument is
Some new developments in the field of micro-CMMs,
capable of achieving uncertainties of the order of
as, e.g., the Zeiss F25 already touch the interesting
U = 25 nm for cylindrical parts.
measurement uncertainty class of U = 100 nm and
below, but probe system geometries severely constrain
the axially reachable surface to some few mm [5].
Specialised form measurement and 1D length
measurement instruments can achieve expanded
uncertainties below 10 nm. Therefore, PTB has
calibrated piston-cylinder assemblies with these
instruments for more than two decades.
3.2 Form measurement instruments
For roundness measurements with the lowest
achievable measurement uncertainty, a modified RTH
Talyrond 73 operated in multi-step error separation
Fig.4 Functional schematic of PTB's reference Abbe
mode is utilised. With that instrument, an uncertainty of
comparator “KOMF”. It is equipped with dual probe and dual
U = 6 nm can be achieved [6].
interferometer.
For combined roundness, straightness and
parallelism measurement a modified MarForm MFU8
3.4 Multi-purpose measurement machine
(called MFU8PTB) is used [7].
MFU110WP
For the dimensional measurement tasks of the
Boltzmann constant project, PTB has extended its
capabilities by a new measurement instrument for
form and size, the MFU110WP [9]. That machine is
equipped with a high speed rotary table and
interchangeable feeler systems. Among these are
systems for both size and form measurements,
and
in addition, special purpose probe systems,
as,
e.g., the probe system 1320D, which is optimized
for diameter measurements. The machine control
eliminates most guide error influences on
measured profiles by internally subtracting
reference data which are gained by capacitive
scanning of an internal metrology frame during
positioning.
Fig. 2 Reference roundness measuring instrument Talyrond
Most cylinder form measurement machines can
73. The image shows the set-up for running the multi-step error
only measure planar, i.e. roundness or axial
separation procedure.
straightness profiles of the cylinders [10]. The
MFU110WP additionally is able to scan the cylinder
helically by moving its rotary table and Z-axis in
parallel [11]. That measurement mode is
advantageous for the numerical calculation of the
effective area of the pressure balances, because it
provides the most complete information on the
piston and cylinder bore topography. However, the
needed measurement time, drift effects, and wear
of the contacting element limit the usefulness of
such a scanning mode when operated by
mechanical contacting.
Fig. 3 Functional schematic of PTB's modified MFU8 cylinder
form measuring instrument with an additional plane-mirror
interferometer.
15
3.5 Measurement set-up and artefact clamping
The precision of the dimensional calibration strongly
depends on the reproducibility of the measurement
positions. This is especially important when more than
one measurement instrument is used for the full
calibration procedure. Therefore, special artefact
clamping tools based on kinematical mounts were
manufactured. They enable an easy and reliable
positioning of the artefact to be measured.
The system is based on clamping disks with
kinematic mounts (fig 8-9). These ensure a fast and
reliable positioning. The kinematic mounts consist of
precision rollers in the 120° positions of a circle which
are glued to the clamping disks and their counterparts at
the rotary tables of the MFU110WP and KOMF which
Fig. 5 Form and size measuring instrument MFU110WP at
are composed of a pair of balls. A notch-nose pair
PTB's clean room facility.
breaks the 120° symmetry and thus ensures a correct
polar positioning.
To overcome this limit, the MFU110WP features an
The MFU110WP rotary table is equipped with a
additional optical feeler system based on a heterodyne
quick clamping mechanism which allows a clamping
white light interferometer, which can acquire data with
disk exchange within seconds (see fig 10). In fig. 11, a
high speed. This system makes it possible to scan a full
mounted clamping disk with a piston and a second
cylinder surface with high data density within less than a
clamping disk with a cylinder are shown. The second
minute [11]. Of course, such high speeds should be
clamping disk was put near to the rotary table to achieve
avoided when the stability and noise level of the
thermal equilibrium between the artefact and the
measurement signal has to be very low as it is in the
measurement machine.
case of application in the Boltzmann project. But even
T h e t e m p e r a t u r e s o f a r t e f a c t s d u r i n g
under these demands, the speed gain of the optical
measurements can be measured by Pt100 resistance
measurement is significant and helps to avoid drift
thermometers that are read out through sliding contacts
influences which become dominant with longer
in the rotary table. These thermometers are not
measurement durations.
calibrated. Therefore, they are compared to calibrated
Pt100 thermometers that can be applied to the artefact
during the standstill of the rotary table.
A major uncertainty source in earlier measurement
procedures for piston-cylinder assemblies was the
restricted reproducibility of the Z-position of the
measurement, especially when moving the artefact
from one measurement machine to another. The
Z-component of the artefact coordinate system is of
greater importance for the application, because piston-
cylinder assemblies have to be paired for pressure
measurement. The effective area has to be calculated
for the paired system. Therefore, reference spheres
were mounted to the clamping disks coaxially with the
Fig. 6 Optical probe “WhitePoint” measuring the inner surface
artefacts (fig. 12). They can be contacted by both optical
of a pressure gauge cylinder. The swivel axis is positioned to
and tactile probe systems of different measurement
the 0° position, such that the 90° beam of the probe is enabled.
machines and thus may be used for identifying a certain
Z-position.
Fig. 7 WhitePoint probe measuring the outer surface of a
pressure gauge piston. The swivel axis is positioned to the 45°
position to enable the 45° beam of the probe system. This
measurement geometry allows the scanning of the artefact
Fig. 8 Schematic drawing of a MFU110WP clamping disk for
with less geometrical constraints than at the 0° swivel axis
piston-cylinder assemblies. Left: upper face; Right: lower
position and is more stable than the 90° position.
face
16
4. CALIBRATION PROCEDURE PERFORMANCE
TESTS
PTB has data records for certain piston-cylinder
assemblies at its disposal which go back up to 20 years.
During that time some assemblies were measured
repeatedly by different machines and measurement
procedures, including different error separation
techniques. These artefacts are very well-known and
consequently were selected to compare the results of
the MFU110WP with those of the other machines. In
addition, first measurement repeatability checks at the
new artefacts were accomplished.
One of the piston-cylinder assemblies (abbr. “PCU”)
2
with long measurement history is a 5 cm unit identified
by serial number 6222. It was used to study consistency
Fig. 9 Lower face of a clamping disk. The three rolls for the
between results of the new MFU110WP machine and
kinematic mount are visible at the 120° positions. The notch fits
into a nose of the rotary table and fixes the rotational
those of other dimensional measurement instruments.
orientation.
Another assembly measured with the MFU110WP
2
was a 20 cm unit identified by serial number 1162,
which is one of the six piston-cylinder assemblies to be
used in the experiments for the re-determination of the
Boltzmann constant. This unit was very new and was
dimensionally studied at PTB for the first time.
Both piston-cylinder assemblies are made of a
tungsten carbide material, each have a different design
and were manufactured by DH-Budenberg, France (unit
6222) and by DH Instruments, USA (PCU 1162).
reference sphere
measured area
+24 mm
0 mm
60
-24 mm
Fig. 10 MFU110WP rotary table with double pairs as kinematic
bearing counterpart and quick-clamping mechanism for the
clamping disks. The cables are connected to Pt100 resistance
thermometers.
100
Fig. 12 Schematic drawing of the measured area of the piston
and the cylinder. The coordinate system is common to both
artefacts. The positions of the Z-coordinate reference spheres
are indicated. These spheres are utilised to transfer the axial
origin of the coordinate system between different instruments.
4.1 Form measurements
Form measurements of known assemblies were
repeatedly performed with the MFU110WP with both
tactile and optical probing. The resulting data were
analyzed with respect to noise, stability, reproducibility,
and comparability to the historic data. It was found that
optical contacting leads to the most stable results, at
Fig. 11 In the background: Piston with clamping disk mounted
least under the high quality environmental conditions in
to the rotary table of the MFU110WP. In the front: Cylinder
which the machine is operated. Therefore, only the
mounted to clamping disk in waiting position. In this position,
optical data are used for further discussion.
the next artefact to be measured can be left until thermal
For comparability to historic data, all straightness
equilibrium with the machine is achieved.
profiles were filtered with a Gaussian low-pass filter with
a 0.8 mm cut-off length. All roundness profiles were
filtered with a low-pass, with a cut-off wave-number of
150 UPR (the filters were implemented as described in
17
DIN EN ISO 11562 [12]). The form profiles of common
piston-cylinder assemblies generally don't carry
significant harmonic content for cut-off lengths lower
than 2.5 mm or wave-numbers greater than 50 UPR.
Therefore, a stronger filtering could be applied without
information loss. This might be an option for future data
evaluations. The measurement uncertainty of form
profiles is tightly connected to the filtering: Stronger
filtering means lower uncertainty [13]. Here is a limited
source, therefore, for uncertainty improvement.
In fig.13, the straightness reference calibrations of
four generatrices of piston PCU 6222 are shown. All
straightness deviations amount to approx. 0.1 µm in
conjunction with a parallelism deviation less than 0.2
µm. This means that this piston-cylinder assembly is
one of the best quality cylindrical artefacts which has
ever been measured at PTB. For that artefact, PTB has
a measurement history available of nearly 20 years. The
data of fig.13 was gained by applying the reversal
method [14]. That method is notably time-consuming
and took some weeks to be completed. The calibration
dated from 2006.
The same generatrices were measured with the
MFU110WP system in optical and tactile mode. These
data took only some minutes per measurement cycle to
be acquired. The corresponding optical data are shown
in fig. 14. They are identical to the tactile data. In
Fig. 13 Reference straightness profiles of the four generatrices
general, the profiles agree well with the reference.
0°, 90°, 180° and 270° of the piston of assembly PCU 6222.
However, near the axial measurement position 10 mm in
The measurement was performed with the MFU8PTB in
the MFU110WP profiles, there are apparent local
reversal mode.
straightness deviations which are not visible in the
reference profiles. This is possibly a measurement
artefact which stems from a non-perfect calibration of
the MFU110WP metrology frame. This effect only
slightly affects the straightness and parallelism
parameters.
For the purpose of scanning at generatrices, the
probe shaft may be positioned vertically, i.e. to the 0°
position of the swivel axis (fig. 6). This is the mode of
choice for inner cylinder surfaces. This geometry
requires shaft lengths that allow complete penetration
into the cylinder without touching the upper front face
with the probe clamping or swivel axis housing or - when
used for pistons - to travel completely down over the
piston's generatrix. But there are limits for the shaft
length which stem from rigidity and vibration insensitivity
requirements.
The MFU110WP swivel axis can be positioned to
any inclination angle. Therefore, for piston
measurements the required shaft length may be chosen
smaller. This is important, because the piston of most
piston-cylinder assemblies is much longer than the
cylinder.
For the optical probe system, the inclination angle
has to match the angle of an optional second laser
beam, if available (see fig. 7).
Fig. 14 Straightness profiles of piston PCU 6222 acquired
with the optical probe of the MFU110WP.
18
Figs. 15 and 16 show roundness profiles at various
axial measurement positions of the same artefact
measured by the MFU8PTB and the MFU110WP in
optical mode (short helical integration was applied [11]).
The calculated roundness deviations are of the order of
45 nm. It is obvious that the roundness varies only
slightly with the axial position. The MFU110WP profiles
show much less “waviness” than the MFU8PTB profiles.
The apparent waviness is mainly caused by the spindle
error of the MFU8PTB. However, in this case the
MFU8PTB data are not the reference calibration data.
The reference calibration was performed by using a
Talyrond 73. The profiles such achieved carry an even
lower noise level and because the error separation
technique utilised with the Talyrond additionally enables
nearly perfect elimination of the spindle error. The
resulting roundness deviations amount to 25 nm only
(see fig.17). But because the measurement of
straightness profiles is much more demanding than
roundness measurements and thus is associated with
larger measurement uncertainties the resulting
Fig . 16
Superposed roundness profiles measured with the
uncertainty of the 3D data set of the piston-cylinder
optical probe of the WP110WP at the same axial positions as
assemblies will not be limited by the roundness
above. The apparent roundness deviations amount to approx.
uncertainty. Furthermore, for the Talyrond the clamping
45 nm.
disks cannot be used and the Z-position is uncertain to
at least 0.5 mm, because it cannot be positioned CNC-
controlled. It seems, therefore, more practical and
0,1 µm
targeted with respect to the overall measurement
uncertainty to use the optical data of the MFU110WP for
the calibration of piston-cylinder assemblies.
Fig . 17
Reference roundness profile measured with
Talyrond 73 of one of the axial positions as measured in fig.16 .
The roundness deviation amounts to 25 nm.
In fig.18, a 3D representation of the piston PCU
6222 surface is shown. These data were gained by
applying the MFU110WP optical helical scan mode. The
data were not filtered, because so far there is no widely
accepted or even standardized multi-dimensional filter
algorithm available. In principle, data sets like this
Fig. 15 Superposed roundness profiles measured with the
should be superior to line scans with respect to piston-
MFU8PTB at different axial positions of the piston PCU 6222.
cylinder calibration, because they carry topographic
The apparent roundness deviations amount to approx. 60 nm.
information about the full cylinder surface. However, so
far there is no algorithm to integrate the independently
measured diameter information. Therefore, the directly
measured full 3D data set can only be dealt with as
additional information.
19
20
15
10
KOMF-2006
m
m
5
LAKO-1995
/
n
i
t
i
o
MFU8 2006
s
0
o
p
l
MFU110_Dia-2008
i
a
x
-5
A
-10
-15
-20
24984.6
24984.7
24984.8
24984.9
24985.0
24985.1
Diameter/ µm
Fig. 18 Helical scan of the full surface of a pressure
Fig. 19 Cylinder PCU 6222 diameter measurement
gauge piston performed with the optical probe
comparison. The data stems from four different instruments.
system.
The instruments and calibration years are specified. The
MFU110 data was measured with the diameter probe 1320D.
4.2 Diameter measurements
All results agree with the uncertainty U = 50 nm of the reference
calibration (KOMF).
For the full calibration of the piston cylinder
assemblies, diameter measurements are needed.
Unfortunately, at the project start of the Boltzmann
20
LAKO-1995
project the KOMF was temporarily not available due to
t e c h n i c a l p r o b l e m s . T h e r e f o r e , d i a m e t e r
15
MFU8-2006
measurements were performed with the MFU110WP by
KOMF-2006
10
using the diameter probe system 1320D. The KOMF will
m
m
MFU110_Dia-
be used after re-adjustment to verify the MFU110WP
/
5
2008
n
data.
i
t
i
o
In figs. 19 and 20 , the diameter calibration history of
0
s
o
the piston-cylinder assembly PCU 6222 (material:
p
l
-5
-6
-1
tungsten carbide, a
= 5*10 K ) is compared to the
i
a
x
diameter results of the MFU110WP with the probe
A -10
1320D. The data stems from a MFU8PTB measurement
-15
in 2006, a KOMF measurement in 2006, and a LAKO
measurement in 1995. The LAKO was PTB's former
-20
diameter reference instrument. The common expanded
24984.0
24984.1
24984.2
24984.3
measurement uncertainties U = 50 nm of the KOMF
reference data are marked by error bars. That
Diameter / µm
uncertainty assumption is quite large for the capabilities
Fig. 20 Piston PCU 6222 diameter measurement comparison.
of the KOMF [15]. However, in 2006, the clamping disks
Nearly all nominal results are within the uncertainty U = 50 nm
were not yet available and such additional uncertainty
of the reference calibration (KOMF).
contributions were introduced to account for the more
difficult measurement position identification. It is
assumed that future KOMF measurements at piston-
5. DATA EVALUATION
cylinder assemblies can achieve uncertainties in the
range of U = 20 nm to 25 nm. Nearly all nominal
To generate 3D data sets describing the topography
diameter results agree with the KOMF data. When a
of the piston and the cylinder bore, straightness
measurement uncertainty of U = 60 nm is assumed
deviations (S) and roundness deviations (R) are linked
for the MFU8PTB, of U = 40 nm for the LAKO, and
to diameters (D).
U = 50 nm for the MFU110WP-1320D, all data are
The choice of the linking procedure is important
compatible. These results also prove the outstanding
because, apart from the uncertainty of S, R and D
long-term stability of the piston-cylinder assemblies,
measurements, the discrepancies between the linked
which always get in mechanical contact during the
data is a contribution to the uncertainty of the 3D data.
pairing process.
So far [16], only two pairs of diameters, measured in
Thus the diameter measurement capabilities of the
two reference levels and in two orthogonal directions,
MFU110WP are at least sufficient for first quality checks
have been used for a 3D data generation which was
of the Boltzmann project assemblies and to monitor
performed successively: First, two roundness traces,
possible changes during the lifetime of the project.
measured in the reference levels, were linked to the two
Because the MFU110WP can measure diameters about
diameters pairs; then the generatrix traces were
one decade faster than the reference machine KOMF,
positioned in the space to meet the defined two
this result helps to save time or allows more repeat
roundness traces; finally, the remaining roundness
measurements.
traces were adjusted to the generatrix traces. To
20
improve the consistency of 3-dimensional data, a new
12492600
PCU 6222 - tactile
approach based on the least-squares method has
12492500
recently been developed [3] which allows the S, R and D
data to be linked with each other with only minimum
12492400
discrepancies between them. When processing the
dimensional data, it is possible to weight them,
m 12492300
n
/
diameter 0°
diameter 90°
depending on their measurement uncertainties.
i
i
straightness MFU8
roundness MFU8
d 12492200
After the 3D data sets have been generated, they
r
a
straightness MFU110
roundness MFU110
are transformed to a new coordinate system, in which
12492100
the z-axis coincides with the axis of the LS cylinder of the
3D data found by the method described in [17]. This step
12492000
is important to achieve a coaxial positioning of the 3D
data sets for the piston and the cylinder bore.
12491900
-20
-16
-12
-8
-4
0
4
8
12
16
20
The effective area of the piston-cylinder assemblies
z / mm
is calculated by the Dadson theory [1] which, for gas
operated piston-cylinder assemblies, assumes a
12492600
PCU 6222 - optical
viscous flow in the piston-cylinder gap, with the gas
12492500
obeying the ideal gas flow, and leads to the expressions
given below:
12492400
r
l
0
p
d r
æ
ö
p
p
d
A
r
=
p
+
ç
÷
+
m 12492300
n
diameter 0°
diameter 90°
0
p (
)
0 rc (
)
r
0
p
c
d z
(1)
p
p
z
-
d
ò z
ç
d z ÷
/
1
2
i
i
straightness MFU8
roundness MFU8
0
è
ø
d 12492200
straightness MFU110
roundness MFU110
0.5
r
a
é
z
l
d x
d
ù
x
2
p
p
p -
+
=
p
(2)
z
1
(
2
ê
2
)
2
1
ú
ò
3
ò
12492100
ê
r -
r
r -
r
0 (
c
p )
3
0 (
c
p )
ú
ë
û
12492000
Here r and r are the piston and cylinder radii, p and
p
c
1
p are the measurement and ambient pressures, p is
12491900
2
z
the pressure distribution in the piston-cylinder gap, and l
-20
-16
-12
-8
-4
0
4
8
12
16
20
z / mm
is the length of this gap. Equations (1) and (2) furnish the
Fig. 21 Gap profile between piston and cylinder of the (virtually)
effective area for one particular pair of the piston and
paired assembly PCU 6222 measured with MFU110WP tactile
cylinder generatrix line. They are applied for all possible
a) and optical b) probe compared with the data obtained with
combinations of the piston's and cylinder bore's
MFU8. The vertical scale divisions amount to 100 nm.
generatrices, and, finally, the average of all calculated
effective areas is taken.
24984400
PCU 1162 - MFU110
6. RESULTS AND DISCUSSION
24984300
First measurements were performed at piston-
cylinder assembly PCU 6222 with the MFU110WP
24984200
included, along with a 3D scan, determination of
m
n
straightness and roundness, but not diameters. For this
/ 24984100
i
i
d
reason, to create 3D data sets, the straightness and
r
a
roundness deviations data were linked to the diameters
24984000
previously determined with the MFU8 machine.
diameter 0°
diameter 90°
24983900
straightness tactile
roundness tactile
6.1. 3D link results
straightness optical
roundness optical
24983800
The 3D evaluation results of the tactile and optical
-20
-16
-12
-8
-4
0
4
8
12
16
20
measurements with the MFU110WP are shown in
z / mm
comparison with the older data obtained with the MFU8
Fig. 22 Gap profile between piston and cylinder of assembly
in fig.21 . The graph illustrates the gap geometry of the
PCU 1162 measured with MFU110WP tactile and optical
virtually paired piston-cylinder assembly. The gap has
probe.
an extent of approximately 200 nm. The new results,
both obtained by tactile and optical measurements, are
very close to the old data with the exception of the small
measurement artefact at the straightness profiles
6.2. Uncertainty of 3D data
already mentioned in section 4.1.
The uncertainty of the 3D radial values generated by
Also, for assembly PCU 1162 we observed quite
a link of diameter, straightness, and roundness data is a
good agreement between the tactile and optical data, as
combination of their uncertainties with the final
well as between the common points of the diameter,
discrepancies of the radii of the generatrices and
straightness, and roundness measurements. The
roundness traces as well as the diameters at the
straightness profiles reveal some stronger waviness
common points. At this stage it is not possible to make a
than in the case of assembly PCU 6222 which evidently
solid claim for the uncertainty of the diameter,
reflect real properties of both assemblies (see fig. 22).
straightness and roundness measurement performed
The gap of this unit is much narrower than that of PCU
with MFU110WP. However, as it was discussed in [18]
6222. It amounts to less than 50 nm in the centre.
an estimation of the radii uncertainties for generatrix and
21
circle traces, u(r ) and u(r ), can be done using the expressions
S
R
(3)
u (
r
u D
=
r
+
d
r
+
d
S ) (
)
[ 2]
2
2 (
D S )
2
-
(
R S )
0 5
.
-
(4)
u (
r
u D
=
r
+
d
r
+
d
R )(
)
[ ]
{2 2
2
(
D R )
2
-
(
R S )
}
0. 5
-
where u(D) is the uncertainty of the diameters, and (r ), (r ) and (r ) are the differences between the diameter and the
D-S
D-R
R-S
straightness, the diameter and the roundness, and the roundness and the straightness data, respectively.
The uncertainty estimation results are presented in Table 1. Compared with the measurements performed on unit PCU
6222 with MFU8 and Talyrond 73, measurements with the new MFU110WP furnish discrepancies which at the moment are
higher by a factor of two to three. This results in the higher uncertainties of the radial values and of the effective areas. The
measurements with the tactile and optical probes have approximately the same performance.
Table 1
Summary of the dimensional measurements and evaluation for piston-cylinder assemblies PCU 6222 and PCU 1162: artefact
measured – cylinder (c) and piston (p); property (X) – diameter (D), roundness (R) and straightness (S); instrument applied for dimensional
measurement; standard measurement uncertainty of property X (u ); differences between half diameters, R and S radii (Y); standard
X
deviations of these differences [(r )]; standard uncertainties calculated for R and S radii [u(r )]; their contributions to the effective area
Y
X
uncertainties [u (A )/A ] and [u (A )/A ]; the effective areas (A ) and their combined standard uncertainties determined from the dimensional
r,R
0
0
r,S
0
0
0
data [u(A )/A ].
0
0
22
For the diameters of assembly PCU 1162 measured
6. CONCLUSION
with MFU110WP, a standard uncertainty of 40 nm was
A procedure for the dimensional calibration of
estimated which will have to be verified in the future. The
piston-cylinder type pressure standards has been
discrepancies and the combined uncertainties of the
described. It was shown that the new instrument
radial values are very similar to those for assembly PCU
MFU110WP significantly improves the efficiency of the
6222.
procedure. With respect to the quality of the
measurement and the achievable uncertainty, the
6.3. Effective area
following may be concluded:
The effective areas calculated using equations (1)
and (2) for different dimensional data sets and the
-
The determined effective areas based on tactile
associated combined standard uncertainties are
and optical measurements with MFU110WP are
presented in the two last columns of Table 1. The
equivalent. This justifies application of the optical
following uncertainty contributions were taken into
technique for shape deviation measurements.
account: uncertainty of the 3D data sets, standard
-
Roundness measurements are sufficiently good.
deviation of the effective area values calculated for
-
Straightness measurements require improvement
different combinations of the piston and cylinder
(characterization/improvement of the internal
generatrix lines, and the change of the effective area
reference frame, application of the reversal
with pressure.
technique, …).
For assembly PCU 6222, the relative difference
between the effective areas based on dimensional data
-
Diameter measurements with the KOMF are
measured with the MFU110WP tactile and optical
necessary, they will also allow a conclusion about
-8
probes is equal to only 6·10 . The relative difference
the diameter measurement capability of
between the older and the new effective areas is equal
MFU110WP.
-7
to 2.8·10 . Such a good agreement is not really
-
After having reached the appropriate performance
surprising because the new shape deviations measured
of MFU110WP in separate roundness and
with MFU110WP were linked to the diameters
straightness measurements, the instrument's top
measured with MFU8, the same diameters which were
helical scan capability can be used to get extended
used for the calculation of the old effective area.
information about the topography of the piston and
However, the uncertainty of the effective area based on
the cylinder bore.
the MFU110WP data is larger than that of the old
effective area because of larger discrepancies between
REFERENCES
the straightness and roundness data. The latter are
evidently caused by the not yet optimal performance of
[1]
R.S. Dadson, S.L. Lewis, G.N. Peggs, The
the new instrument in straightness measurement mode,
Pressure Balance: Theory and Practice, London,
because the roundness measurements, as stated in
HMSO, 1982.
section 4.1, appear to be very good.
[2]
J. Fischer, B. Fellmuth, J. Seidel, W. Buck,
For assembly PCU 1162, the relative difference
Towards a new definition of the Kelvin: ways to go,
between the effective areas based on dimensional data
Proc. of the 9th Symp. on Temperature and
measured with the MFU110WP tactile and optical
Thermal Measurements in Industry and Science,
-7
probes is equal to only 1.5·10 . In spite of the higher
TEMPMEKO, Dubrovnik- Cavtat, Croatia, 2004,
uncertainty of the diameter measurements carried out at
http:// www.imeko.org/publications/tc12-
unit PCU 1162 with MFU110WP than the uncertainty of
2004/PTC12-2004-PL-002.pdf
MFU8 used for measuring diameters of unit PCU 6222,
the relative uncertainty of the effective area of the first
[3]
W. Sabuga, Towards 7 MPa pressure standards
-6
piston-cylinder assembly is smaller, which is explained
with 1·10 uncertainty. MAPAN – J. of Metrology
by the fact that its nominal effective areas are four times
Society of India, 22 (2007) 3-1
as large as that of unit PCU 6222.
[4]
W. Sabuga, G. Molinar, G. Buonanno, T.
Even though these very first measurements with the
Esward, J.C Legras, L. Yagmur, Finite Element
new instrument MFU110WP have resulted in the
Method used for calculation of the distortion
-6
effective area's relative standard uncertainty of 2.5·10 ,
coefficient and associated uncertainty of a PTB 1
-6
the target uncertainty of 1·10 appears to be achievable
GPa pressure balance – EUROMET project 463,
when the MFU110WP performance in straightness
Metrologia, 43 (2006) 311-325
measurements is improved and, additionally, the
diameters are measured using the reference length
[5]
M. Neugebauer, F. Härtig, O. Jusko, U.
comparator KOMF.
Neuschaefer-Rube, Recent developments in
micro CMM measurement technique at PTB,
ACME Workshop on Coordinate Metrology 2008,
Windsor, Canada
[6]
M. Neugebauer, Uncertainty analysis for
roundness measurements by the example of
measurements on a glass hemisphere, Meas. Sci.
Technol. 12 (2001) 68–76
23
ENABLING STANDARDS FOR NANOMATERIAL CHARACTERIZATION
1
2
1
3
4
Vincent A. Hackley , Martin Fritts , James F. Kelly , Anil K. Patri , Alan F. Rawle
1. National Institute of Standards and Technology (NIST), Gaithersburg, Maryland, USA
2. National Cancer Institute (NCI), SAIC-Frederick, Inc., Frederick, Maryland, USA
3. Nanotechnology Characterization Laboratory (NCL), SAIC-Frederick, Inc., Frederick, Maryland, USA
4. Malvern Instruments Inc., Westborough, Massachusetts, USA
ABSTRACT
A two-day international workshop was convened recently in order to scope out and address the urgent need for standards to
accurately characterize the physico-chemical and biological properties of engineered nanomaterials. These standards are
needed by industry and regulatory bodies in order to meet requirements for the production, application and lifecycle risk
management of nanomaterial-based products ranging from cancer therapeutics to high-tech coatings and composites. The
current deficiency in the availability of such standards, including both documentary and reference artifacts, is perceived as
limiting the widespread adoption and implementation of nanoscale technologies. Herein is given a brief summary of that
workshop, its findings and recommendations.
INTRODUCTION
characterization, and to lay the foundation for future
work needed to validate measurement protocols and
Sufficient and accurate characterization of the physical
provide precision statements for consensus standards,
and chemical properties of engineered nanomaterials
preliminary findings were summarized for three
(ENMs) and their interactions with biological systems
concurrently executed interlaboratory studies (ILSs)
are fundamental requirements for successful material or
sponsored by the ASTM Interlaboratory Study Program
device design. Similarly, proper characterization of
and organized through E56, the committee on
material properties is a critical component for
Nanotechnology. These studies involved roughly 35
understanding and managing the lifecycle risks posed
participants and demonstrated both the benefits and the
by ENMs to the environment, health and safety (EHS).
difficulties associated with the undertaking of such
Formidable obstacles exist to obtaining adequate
efforts.
characterization. Foremost among these obstacles are
those presented by the lack of relevant reference
KEY STAKEHOLDERS
materials and standardized practices, protocols, and
procedures for test specimen / sample preparation,
Workshop participants, numbering just over 100, were
measurement, and data analysis.
drawn from government, academia and industry, and
represented US and international interests including
In order to accelerate research, development, risk
several national metrology institutes as well as
identification, regulation, and widespread adoption of
international standards development organizations.
nanotechnology, there exists an urgent need to develop
Table 1 gives an organizational breakdown of the
new protocols, practices, and reference materials
participation. Among the sponsors and contributors to
(RMs), and to elevate these to the status of
this workshop were a number of major stakeholders
internationally accepted standards. With this in mind, a
from within the U.S. federal government, including the
workshop was held October 8-9, 2008 on the campus of
F o o d a n d D r u g A d m i n i s t r a t i o n ( F D A ) , t h e
the National Institute of Standards and Technology
Environmental Protection Agency (EPA), the National
(NIST) in Gaithersburg, Maryland. The overarching
Cancer Institute (NCI), the National Institute for
goals of the workshop were to:
Occupational Safety and Health (NIOSH), the National
Institute of Environmental Health Sciences (NIEHS), the
1. Stimulate interdisciplinary discourse regarding
Nanotechnology Characterization Laboratory (NCL) at
ENM characterization needs and issues
NCI-Frederick, the National Nanotechnology
2. Promote cooperation among government
Coordination Office (NNCO), and NIST. The Oregon
agencies and international stakeholders
Nanoscience and Microtechnologies Institute (ONAMI),
3. Accelerate development and validation of
a large academic-based consortium in the U.S., and
protocols, standards and RMs needed to
ASTM International were non-governmental sponsors.
underpin the safe and widespread use of ENMs
The audience was highly interdisciplinary and included
a number of leading scientists working in the
The workshop was organized around an agenda that
nanobiotechnology arena, but also numbered among
included formal presentations, facilitated discussions,
the audience were standards developers, regulators
demonstration of a proposed new electronic medium for
and policy makers. Thus many different perspectives
pre-standard development, and four parallel focused
were represented, providing for robust and lively
break-out sessions. As a starting point for discussions of
discussion and meaningful consensus.
measurement issues associated with ENM
24
OVERARCHING ISSUES
Participants stressed that verifiable science is needed
Nanotechnology is enabling new therapies for fighting
for the assessment of ENM hazards, since there are
cancer, with ClinicalTrials.gov currently listing 59 clinical
significant potential implications for economic
trials for nanoparticle-based cancer therapies.
development and human health. It's critical to
However, nanoparticles frequently cause false positive
accurately assess ENM hazards using reproducible and
and false negative results in currently used in vitro
validated standards and protocols. There are also
assays and they present novel challenges for
unique issues for ENM hazard assessment that must be
characterization. Piotr Grodzinski, Director of the NCI
taken into consideration: e.g., small differences in
Alliance for Nanotechnology in Cancer, discussed the
nanoparticle size can dramatically influence results.
need for, and NCI's efforts to establish, a framework for
Reproducibility in biological testing of ENMs is possible
the clinical translation of cancer nanotechnologies. A
but challenging; it demands careful control of all
key component of this framework is standardization of
parameters, standardized protocols, well-characterized
analytical protocols for physical, in vitro and in vivo
materials, and careful laboratory practice. The
testing of ENM-based diagnostic, imaging and
International Alliance for NanoEHS Harmonization
therapeutic platforms.
(IANH), chaired by Ken Dawson of University College
Dublin (Ireland) will conduct round-robin studies to
Potential exposure to free ENMs is likely greatest for
validate existing toxicity assessment strategies and
those who manufacture and process these materials.
thereby improve reproducibility and overall confidence
Aleksandr Stefaniak of NIOSH stressed that current
in reported results.
methods and protocols for risk assessment of ENMs in
an occupational exposure scenario are not well
An industry perspective on nanotechnology standards
established; biologically relevant metrics, suitable RMs,
and needs was provided by representatives from Intel
validated exposure assessment tools, and validated
Corporation, Eli Lilly and Company, and Thermo Fisher
protocols are needed in order to make progress in
Scientific. It was emphasized that knowledge is critical
addressing occupational exposure risk assessment. A
to enable effective life-cycle risk assessment and
few guides now exist that address worker health
management, and this requires an understanding of the
protection, including contributions from BSI British
principles of nanoparticle-biological interactions and
Standards, NIOSH and ASTM International. Standards
nanotoxicology. The need for well-characterized high
for data management are also lacking; for example, a
purity ENMs and RMs for reliable toxicological and
national exposure database for nanotechnology
physical characterization tests was stressed, as was the
workers and/or medical registry would require a
need for biological testing protocols that deliver
standardized framework for materials identification and
reproducible results and standardized biological media
data input.
for assays. Without these tools in place, uncertainty with
respect to potential hazards and liabilities limits
Reference material development involves a balance of
commercial development and deployment of ENM
four factors, as described by Steve Hankin of the
products.
Institute of Occupational Medicine: 1) needs of the
c o m m u n i t i e s , 2 ) c h o i c e a n d r e l e v a n c e o f
Key research needs include: a standardized testing
physicochemical properties, 3) availability and
strategy for assessing toxicity, determination of the best
suitability of materials, and 4) characterization ability.
metrics for assessing particle toxicity, exposure
There is a need for the community to define questions
monitoring methodologies, and risk assessment
that RMs might help solve; these are thematically stated
methodologies. In terms of dose metrics, mass is the
by the UK Nanotechnology Research Coordination
most commonly used, but size, surface characteristics,
Group (NRCG) and US National Nanotechnology
etc. may be more biologically relevant. There is
Initiative (NNI), but there is currently no consensus on
currently wide variability in reports of toxicology for the
specifics. REFNANO 2007, Organization for Economic
“same” materials, and a wide variability in the types of
Cooperation and Development (OECD) 2008 and
characterization and properties of the ENMs used in
NanoImpactNet 2009 have or will nominate and
reported studies. Most importantly, it has not yet been
prioritize candidate materials (e.g., TiO , gold, silver,
established that current testing protocols correlate with
2
polystyrene, carbon nanotubes are common
acute toxicity and/or chronic effects.
suggestions).
Reference materials are also needed for instrument
The field of nanotoxicology will require advancements in
qualification and quality control in a manufacturing
physical measurement capabilities, including the
environment, where size characterization is of critical
development of metrics for surface properties,
importance for drug development since nanoparticles
capability to characterize and detect nanoparticles
are being engineered to perform pharmaceutical
across a variety of biological and environmental media,
functions that depend on their size. Standards
characterization of agglomeration and aggregation,
producers must be reputable, provide complete and
capability to differentiate the shape and aspect-ratios of
c l e a r s u p p o r t i n g d o c u m e n t a t i o n , a n d u s e
particles in mixtures, and discrimination between
techniques/methods that are accepted by the industrial
engineered and background nanoparticles. These
community. Both physical and documentary standards
advancements will need to be supported by
have finite lifetimes based on their applicability, and the
d o c u m e n t a r y s t a n d a r d s t h a t d e f i n e t h e i r
lifetimes of physical standards are also limited by their
implementation across labs.
shelf-life/stability. These issues may be particularly
25
relevant for the fast evolving field of nanotechnology,
Table 2), but with some clear outliers. Not surprisingly,
and for many ENMs that are unstable or reactive.
the smaller test materials (10 nm or less) exhibited the
greatest variance. There were differences in the
In the U.S., medical devices are classified and regulated
interpretation of micrographs between laboratories,
according to the degree of risk to the public (Classes I-
especially with regard to identification of individual
III, with III requiring the most stringent regulation). Use
particles. Plans include a post-study analysis of the
of FDA-recognized standards improves the quality of
imaging data to assess the impact of different image
510(k) applications and facilitates the regulatory
analysis algorithms. The precision statement for E2490
process. Challenges remain for regulating nano-
was recently approved by committee ballot.
enabled medical devices, including development of
standards for identification and assessment of ENMs in
The two biological studies included nine participants in
products and for biocompatibility and toxicity
ILS201 (hemolysis) and six in ILS202 (cytotoxicity), and
assessment. The FDA is specifically interested in ways
demonstrated the challenge of obtaining reproducible in
of determining if a product contains nanoparticles, and if
vitro biological test results for ENMs across different
the inclusion of ENM changes the product classification.
laboratories.
ISO technical committee 229 on Nanotechnologies is
now working on establishing methods for determining
The preliminary results for ILS201 showed that the
nanoparticle release from ENMs (e.g. by abrasion and
protocol was successful in all participating laboratories,
erosion).
and that obtaining whole blood from commercial
sources in a timely manner and in sufficient quality is
The emerging role of academic institutions in
achievable. Only one out of nine participating labs
nanotechnology standards development was
reported a problem with the quality of the whole blood,
discussed. According to Stacey Harper of ONAMI,
where the plasma free hemoglobin (PFH) value is out of
academics have a different perspective on standards
specification. The overall assay performance, as judged
development since they can investigate libraries of
by precision and accuracy of the standard curve and
ENMs that may not be of immediate interest to industry
quality controls, was also successful. But determination
or suitable for certification as RMs. This perspective can
of the hemolysis caused by nanomaterials was
be utilized, though, in an integrative approach in
complicated by the fact that several participating
collaboration with industry and government partners to
laboratories did not follow the protocol as written.
further the cause of standards development.
ILS202 was conducted for measurement of
nanoparticle cytotoxicty to human hepatocarcinoma
THE ROLE OF INTERLABORATORY STUDIES
cells and porcine renal proximal tubular cells by two
methods: MTT reduction and LDH enzyme leakage.
ASTM International is a consensus standards
Only the MTT data was presented at this meeting. Only
development organization that operates on an
one toxic nanoparticle (the cationic dendrimer) was
individual participatory model. Their Interlaboratory
included in the study, but only two labs saw enough toxic
Study Program was formed in 2005 with an initial
response to estimate an IC50 (50% inhibitory
investment of $4 million USD to provide support for
concentration) for this particle.
organizing studies to develop precision and bias
statements for ASTM standards. ASTM E56 committee
Valuable lessons were learned from these exercises: (1)
on Nanotechnology has approved seven standards thus
a protocol training step should be included before the
far; three of which have been associated with
formal blinded validation is attempted, (2) RM
interlaboratory studies discussed at this workshop:
nanoparticles with low-dose toxicity are needed to
E2490-08 Measurement of Particle Size Distribution of
evaluate cytotoxicity assays, (3) complexity of biological
Nanomaterials in Suspension by Photon Correlation
protocols requires additional guides for users to follow,
Spectroscopy, EE2526-08 Standard Test Method for
such as a schematic or video training, (4) true blinded
Evaluation of Cytotoxicity of Nanoparticulate Materials
study is not feasible for nanomaterials – knowledge of
in Porcine Kidney Cells and Human Hepatocarcinoma
the sample material is an important component of
Cells, and E2524-08 Standard Test Method for Analysis
sample preparation (e.g. adjusting sample pH to
of Hemolytic Properties of Nanoparticles.
physiological range), and this is the step with which
most labs participating in ILS201 had difficulties. and (5)
The interlaboratory studies were conducted through the
access to well-characterized common test materials
E56.02 subcommittee on Characterization: Physical,
and RMs are critical for such studies. Plans to repeat
Chemical, and Toxicological Properties. The studies
these studies in the future are currently under
utilized three NIST gold nanoparticle RMs, and cationic
consideration.
and neutral dendrimeric nanoparticles. A total of 26
laboratories participated in ILS166, which tested widely
Additionally, a number of important issues were raised
used nanoparticle size measurement techniques
with respect to interlaboratory testing and protocol
including photon correlation spectroscopy (PCS; also
development. For instance, there are many sources of
known as dynamic light scattering, DLS), atomic force
variability in cell-based assays, and these should be
microscopy (AFM), transmission electronic microscopy
explored more quantitatively in order to address overall
(TEM) and scanning electron microscopy (SEM), and
inconsistencies and to better define the limits of such
produced data necessary to develop a precision
assays. Interference caused by ENMs, especially in
statement for E2490-08. The preliminary results for
colorimetric-based assays, is a common problem that
PCS were generally very consistent (see for example
impacts the variability and accuracy of these tests.
26
Since the principal purpose of interlaboratory studies is
therapy and detection. The effort has focused on three
to identify assays that are reproducible and to validate
areas: (1) measurement science and method
them in multiple laboratories with documentation of the
development related to the physicochemical properties
results, it was concluded that an informal testing
of ENMs, (2) critical data on nanoscale platforms
scenario with fewer participating laboratories may be
submitted to NCL, and (3) development of RMs and
needed prior to formal testing in order to screen for
standards. NIST and NCL have developed assay
potential problems. Such preliminary round robins
protocols for the physicochemical characterization of
would help ensure success and efficiency in larger scale
ENMs; these protocols will be available on the NCL
formal testing.
website: http://ncl.cancer.gov.
Finally, the principal contributing factor for variability in
The OECD sponsorship program for the testing of
interlaboratory testing and protocol validation involving
manufactured nanomaterials is an example of one
ENMs is most likely sample preparation (i.e.,
mechanism that serves both interagency and
introduction of ENMs into the test medium). There is a
international cooperation. In this program there must be
general lack of validated dispersion protocols at the
agreement on which properties to measure and how to
present time, and a poor understanding of the
measure them, characterization implications of sharing
dispersion process and its impact on the biological
test samples among sponsors, and consistent reporting
interactions of ENMs. Controlling the effective
of test results. The OECD program is designed to
concentration and dose is critical to obtaining accurate
provide the information needs for decision makers
and reproducible assay results that are meaningful with
regarding the environmental, health and safety
respect to risk assessment.
assessment of ENMs, by coordinating many
international efforts organized around 14 specific
INTERAGENCY AND INTERNATIONAL
nanomaterials. It provides a framework for interaction
COOPERATION
and improved communication among researchers
working on the environmental and health implications of
The need for cooperation and coordination between
ENMs.
U.S. federal agencies with a stake in nanotechnology
standards was a unifying theme for this workshop.
The Asia-Pacific Economic Cooperation (APEC) nano
Clayton Teague, Director of the NNCO, pointed out that
project was initiated in 2005 and developed a roadmap
scientific standards development is a “tragedy of the
for the characterization of ENMs, including thin films,
commons” in that standards will benefit everyone, but it
latex spheres, nano silver, and carbon-based
is in no one's rational best interest to invest in their
nanoparticles. The analysis of the preliminary
development directly. Furthermore, there is a limited
interlaboratory comparison of nanoparticle size
pool of qualified and willing participants to work on
measurement took place in 2005; this interlaboratory
nanotechnology standards development worldwide,
study had ten participants and used TEM, AFM and
and this resource must be used efficiently for any
dynamic light scattering (DLS) to measure particle size.
progress to be sustained. It is equally important that
In 2006, they revised the testing instructions and re-
nanotechnology standards are based on solid science
attempted the study, this time with 20 participants and
and engineering. Standards not so founded can
using DLS, AFM, TEM and SEM. In 2007-2008, APEC
constrain innovation and entrench inferior technologies
concentrated on the measurement of thin film thickness
(e.g. cell phone networks in the U.S.), and this requires
by SE, SIMS, TEM, XF, XPS, and XRR.
cooperation between stakeholders. NNCO is interested
in supporting the formation of a community of interest to
COMMUNITY-DRIVEN SOLUTIONS
facilitate standards development at the pre-standard
level and urges the SDOs to collaborate with each other
The benefits of using electronic and community-driven
and with individuals and agencies engaged in standards
approaches for acceleration of pre-standard protocol
development.
development and management of interlaboratory
studies was explored in some detail. Currently, there are
Other current interagency efforts directed toward
sufficient electronic means for formal standards
aligning collaborative resources to address
development, document creation and voting (through
nanotechnology health and standards issues were
the SDOs); however the resolution of negative votes is
described. The NanoHealth and Safety Initiative at
tedious and rate limiting. There is also a need for greater
NIEHS is interested in understanding the interaction of
transparency, and to accelerate the standards
engineered nanoscale materials with biological
development process to comply with the urgent demand
systems. The National Toxicology Program (NTP),
for standards in nanotechnology applications.
which is part of NIEHS, is focused on studying
Additionally, this process would benefit by broader
nanoparticle toxicology through a formal nomination
inclusion of technical experts who are outside the SDO
process that includes other agencies such as FDA.
committee structure.
NIST and NCI have signed a memorandum of
understanding to collaborate on measurements and
A collaborative website (Web 2.0) could be used to
standards related to cancer nanotechnologies. This
record comments, dissent, and resolution, to link to
collaboration became fully operational in 2006. The
authoritative documents, and to organize and assist
basic concept behind this collaboration was to leverage
technical discussion and protocol validation. A prototype
NIST's expertise in physical science to address issues
wiki was demonstrated by Raul Cachau of the Advanced
related to the characterization of ENMs for cancer
Biomedical Computing Center at NCI Frederick. A wiki is
27
a software implementation of a social protocol; the
difficult to control and subject to adaptation and change
important parameters are the policies and guidelines
over time.
(how access is controlled, etc.). Points that need to be
considered are access, traceability (IP tracking), data
The primary recommendation from the workshop
curatorship, ease of use, user requirements, data
participants was to foster a community guided effort for
archiving, security (SSL), and notification (email, RSS).
the exploration of laboratory best practices and the
The prototype wiki is proposed to foster collaborative
harmonization of preliminary stage development of
development and testing of protocols prior to entry into
standards for ENM characterization. The prototype wiki
the formal standards development pathway,
is proposed as the primary mechanism for community
discussions of standards issues, identification of ENMs
interaction in three areas:
for validation of protocols including controls, and
formation of a community of interest. SDOs such as ISO
·
development of standard physico-chemical, in vitro
and ASTM could link to the wiki to complete the process
and in vivo assay protocols
of balloting and adopting international standards, once
·
collaboration in interlaboratory tests to determine the
the protocols have been fully vetted and validated. The
reproducibility and repeatability of assays
proposed wiki would also be used to support a
·
development of study materials and RMs required for
community of interest for nanotechnology standards
t h o s e p r o t o c o l s a n d f o r i n s t r u m e n t
development and would be community-driven in content
calibration/qualification
and focus. Public availability of the standards wiki is
planned for the first half of 2009.
Under the recommended plan, letters of intent would be
solicited from U.S. and foreign agencies and institutions
RECOMMENDATIONS AND CONCLUSIONS
wishing to participate in the collaboration. Resources for
operating the wiki would be solicited by the NNCO from
A vital element in the development of an effective and
the Nanoscale Science, Engineering and Technology
validated protocol (or standard practice) is the
(NSET) subcommittee based on those letters of intent.
conductance of an interlaboratory study, commonly
NSET is the interagency body responsible for
referred to as round robin testing. These studies are
coordination of the NNI. Because of NCI's efforts in
necessary to provide estimates of measurement
developing the pilot wiki, it was requested that NCI
precision for a method, and to ensure that test
initially host the wiki to allow rapid development of draft
procedures generate accurate and meaningful results
wiki pages, rules of governance, and solicitation of the
while avoiding potential artifacts. One conclusion of the
letters of intent.
workshop was that consistent measurement results are
difficult to achieve even under the best of conditions,
ACKNOWLEDGEMENTS
and only the greatest care produces valid data. This was
made particularly evident during the presentation of
The authors wish to express their gratitude to the formal
findings from three parallel ASTM E56.02 sponsored
sponsors and supporters of this workshop, specifically
studies.
ASTM, FDA, NCI, NCL, NIEHS, NIOSH, NIST and
ONAMI. In addition, we acknowledge and thank
It was also clear from these studies that biological
Jennifer Hall of NCL / SAIC Frederick for critical help in
protocols are subject to much greater uncertainty
capturing information generated during the workshop.
relative to physicochemical measurements. Physical
We also acknowledge the services of the many
scientists participating in the workshop were surprised
speakers and discussion leaders who contributed
to hear that 20 % or greater variability in biological assay
significantly to the success of this meeting.
results is considered acceptable in most cases.
Operator bias also seems to be a more significant factor
Author Email Contact
for biological testing, probably due in part to the
Vince Hackley (vince.hackley@nist.gov)
complexity and serial nature of many biological assays.
Martin Fritts (frittsmj@mail.nih.gov)
Another important factor is the dependence of these
Jim Kelly (james.kelly@nist.gov)
tests on biological components that are inherently
Anil Patri (patria@mail.nih.gov)
Alan Rawle (alan.rawle@malvern.com)
28
Table 1. Organizational listing of workshop participants.
Governmental Organizations
Non-Governmental Organizations
Academic
Institutions
U.S. Air Force Research Laboratory
Advanced Surface Microscopy Inc.
Cambridge University (UK)
U.S. Army Edgewoo
d Chemical
ASTM International
Central Michigan University
Biological Center
Beckman Coulter Inc.
Emory University
U.S. Department Of Homeland
Bristol-Myers Squibb
G eorgetown University
Security
The Dow Chemical Company
Industrial Technology
U.S. Environmental Protection Agency
Dupont
Research Institute
European Commission Joint Research
Eli Lilly & Company
(Taiwan)
Centre
Evonik Degussa Corporation
North Carolina State
Federal Institute for Materials
FEI Corporation
University
Research and Testing (Germany)
Horiba Instruments Inc.
Oregon Nanoscience and
U.S. Food and Drug Administration
Institute of Occupational Medicine (
UK)
Microtechnologies Institute
U.S. National Cancer Institute
Intel Corporation
University Co
llege Dublin
U.S. National Institute for Occupational
ISO TC229, TC24
(Ireland)
Safety and Health
Luna Innovations
University of California at
U.S. National Institute of Biomedical
Malvern Instruments Inc.
Irvine
Imaging and B ioengineering
Micromeritics Instrument
Corporation
University of Delhi (India)
U.S. National Institute of
Microtrac, Inc.
University of Massachusetts
Environmental Health Sciences
Midatech Biogune S.L. (Spain)
Amherst
National Institute of Advanced
MVA Scientific Consultants
University
of Michigan
Industrial Science and Technology
Pennsylvania Bio Nano Systems, LLC
University of Technology
(Japan)
SAIC Frederick Inc.
Dresden (Germany)
U.S. National Institute of Standards
Thermo Fisher Scientific
Un
iversity of Texas Health
and Technology
Unidym Inc.
Science Center at Houston
National Measurement Institute
United States Pharmacopeia
(Australia)
U.S
. National Nanotechnology
Coordination Office
National Physical Laboratory (UK)
National Resea
rch Council Canada
Oak Ridge National Laboratory
Table 2. Preliminary comparison of results for ILS166, showing mean values for Test Sample B (nominal 30 nm gold).
Measurement
Mean Size and Expanded Uncertainties (nm)
NIST Ref. Value
NIST U*
Mean ILS166
ILS166 U§
AFM
24.9
1.1
25.1
2.4
SEM
26.9
0.1
28.4
8.0
TEM
27.6
2.1
27.3
4.6
PCS¶
28.6 (173º)
0.9
29.4
7.0
26.5 (90º)
3.6
¶
8
NIST reference values for PCS were obtained by a single operator on two instruments operating at two different scattering angles. PCS
results for ILS166 represent multiple measurement configurations, instruments and operators.
* Expanded uncertainties, U , are calculated as U = ku , where u is intended to represent, at the level of one standard deviation, the
c
c
9
combined standard uncertainty calculated according to the ISO and NIST Guides . The coverage factor, k, for 95 % expanded uncertainty
intervals is based on a t multiplier with the appropriate associated degrees of freedom.
§ Expanded uncertainties are calculated as U = ks, where s is the standard deviation of the mean. A coverage factor, k=2, is used to
approximate a 95 % expanded uncertainty interval.
REFERENCES
1 Nanotechnologies – Part 2. Guide to safe handling and disposal of manufactured nanomaterials. BSI British Standards PD 6699-2:2007.
2 NIOSH Current Intelligence Bulletin: Evaluation of Health Hazard and Recommendations for Occupational Exposure to Titanium Dioxide, 2005; Approaches to Safe
Nanotechnology: An Information Exchange with NIOSH, 2006. U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National
Institute for Occupational Safety and Health.
3 Standard Guide for Handling Unbound Engineered Nanoscale Particles in Occupational Settings. ASTM E2535-07.
4 S.F. Hansen, B.H. Larsen, S.I. Olsen, and A. Baun, “Categorization framework to aid hazard identification of
nanomaterials,” Nanotoxicology, 1 – 8 (2008).
5 R.J. Aitken, S.M. Hankin, C.L. Tran, K. Donaldson, V. Stone, P. Cumpson, J. Johnstone, Q. Chaudhry, S. Cash, REFNANO: Reference materials for engineered
nanoparticle toxicology and metrology. Institute of Occupational Medicine (Edinburgh). Final report of study commissioned by the UK Department for Environment, Food
and Rural Affairs (DEFRA), 2007.
6 List of Manufactured Nanomaterials and List of Endpoints for Phase One of the OECD Testing Programme. Monograph No. 6, Series on the Safety of Manufactured
Nanomaterials, Organization for Economic Cooperation and Development, 2008.
7 Skip Rung, Nanotechnology Now, Nanomaterials-Biological Systems Interactions - Addressing the Complexity, October 8, 2008, http://www.nanotech-
now.com/columns/?article=247.
8 Reference Material 8012, Gold Nanoparticles, Nominal 30 nm Diameter, 2008 (Report of Investigation available at https://www-
s.nist.gov/srmors/view_report.cfm?srm=8012).
9
st
Guide to the Expression of Uncertainty in Measurement. 1 ed.; International Organization for Standardization, 1993; see also B.N. Taylor, C.E. Kuyatt, Guidelines for
Evaluating and Expressing the Uncertainty of NIST Measurement Results. Technical Note 1297, National Institute of Standards and Technology, 1994 (available at:
http://physics.nist.gov/cuu/Uncertainty/index.html).
29
HARDNESS MEASUREMENT IN BRAZIL IN THE NANOTECHNOLOGY ERA
.
1
2
3
Renato Reis Machado , Geralda Cristina Durães de Godoy , Margareth Spangler Andrade
1Instituto Naconal de Metrologia Normalização e Qualidade, Duque de Caxias, Brasil
Laboratório de Força – DIMCI / DIMEC / LAFOR, rrmachado@inmetro.gov.br
2Universidade Federal de Minas Gerais, Escola de Engenharia, Departamento de Engenharia Metalúrgica e de Materiais,
Belo Horizonte, Brasil
3Fundação Centro Tecnológico de Minas Gerais, Setor de Tecnologia Metalúrgica, Belo Horizonte, Brasil
Abstract
The measurements of conventional indentation hardness (Brinell, Rockwell, Vickers and Knoop) are known and their methods
were normalized more than 50 years ago. Their results are numbers that represent the size of the residual impressions on the
sample surface after the indentation. Face to scientific and technological demands, noticed in the superficial engineering and
more recently in nanotechnology field, different methods were developed for the characterization of hardness and other
mechanical material properties in micro and nanometer levels. The method known as "Measurement of Hardness and
Materials Parameters for Instrumented Indentation Test” is based on the use of diamond or hard metal indenters to indent the
sample surface, with forces and indentation depths measured and presented simultaneously through a graphic. With this
technique, is possible to characterize the plastic and elastic behavior of a material in nanometer regions (< 200nm), where it
has been frequently the only one which it makes possible the research of nanostructural material, thin film, ceramic material,
etc., independently from hardness. This article has the objective to show the state of the art of nanoindentation tests and the
today activities of some Brazilian research groups in the characterization of the hardness values of the materials in micro and
nanometer level.
Key words: Instrumented indentation, Microindentation, Nanoindentation.
1 This paper is reproduced from the Proceedings of the 1o. CONGRESSO INTERNACIOANAL DE METROLOGIA MECÁNICA, October 8-10,
2008, Rio de Janeiro, Brazil, with permission of its authors and of the Congress organizers.
30
The technology of indentation hardness emerged as a
The uncertainty measurements of an impression with
simple and economic alternative related to the tensile
5m residual diagonal given by a Vickers indenter, for
test, as a way to determine for other manner the value of
example, can be in the order of 20% when used an optic
the mechanical resistance of the materials. The Brinell
microscope for the reading. This uncertainty can grow
hardness method, created in 1900 for Johan August
as the size of the indentation decreases and it can arrive
Brinell (Sweden), appears to attend that need (Dieter,
as high as 100% for impressions with diagonals of 1m
1988).
(Fischer-Cripps, 2002).
The company Wilson Co. (USA) introduced the
Better would be to have a method that could use a
Rockwell hardness method in 1920. This method
indenter like the Vickers one, in a wide scale of test
objectified optimizer some limits of the Brinell method
force, in consonance with an automatic measurement
and, above all, to decrease the time of testing in order to
just like the Rockwell method (Polzin, 1997).
obtain advantages of practical order, turning it, until
today, the method more used by the industry (Low,
2.2. Historical and Establishment of the
2001).
Instrumented Indentation Test
The Vickers method, introduced in 1925 by the Vickers
In 1993 the German institute of standardisation,
Industry Ltd. (England), is strictly related to the Brinell
Deutsches Institut für Normung (DIN), presented to the
method and it is generally used to measure high
technical subcommittee TC 164 SC3 of the International
hardness when the Brinell method is not applicable.
Organisation for Standardisation (ISO), the technical
report TR 14577 in which proposed the establishment of
2. PROPOSAL OF NEW METHOD
a new hardness measurement method, the Universal
Hardness (HU).
The proposal of a new method for hardness and other
material property has to offer advances in relation with
In 1994 the DIN decided after the local industrial
the other current hardness methods. In comparison to
demands that the set of standards sent to ISO by means
the conventional methods, the new one has to (Polzin,
of the technical report TR 14577 should be published
1997):
immediately in Germany. Those standards had the
following numbers and titles: DIN 50359: Universal
· be cheaper, automatic and/or quicker.
hardness testing of metallic materials: “part 1 – Test
· have smaller uncertainties.
method”, “part 2 - Verification of testing machines and”
· bring additional knowledge.
“part 3 - Calibration of reference blocks” (Machado,
· be a unique method for the purpose.
2005).
· give values which can characterize special materials.
· have a standard or a standardization method
This method was based on the use of diamond
established.
indenters like the Vickers (pyramid of square base) or
Berkovich (pyramid of triangular base) to indent into a
As described previously, the methods mostly used for
sample surface with the test forces and indentation
metallic materials are Brinell, Rockwell and Vickers. For
depths measured and presented simultaneously by
Brinell and Vickers, the relevant hardness value is
means of a curved Fxh in the screen of a computer,
determined after the total test force removal. For
figure 1. With this new method, it was possible to
Rockwell hardness, the value is determined through the
characterise the plastic and elastic behaviour of a
measurement of the indentation depth after the
material with minimal operator influence.
additional force test removal and can be done fully
automatically.
Fmax
For the hardness measuring of thin film, thin layer on
compact materials or ceramic, the Rockwell method
cannot be used because its high preliminary and total
40
test forces would influence in the hardness results due
to the crack formation induced during the indentation.
30
)
N
In the Brinell method, the metal ball indenter can cause
F
(
m
differences in the hardness results because it can suffer
20
A
deformation during the test.
B
10
In the Vickers method, all hardness scales are
C
measurable, being a continuous measurement method
and, the application of small test forces are estimable
0
and available in standards, facilitating the measured of
0
50
100
150
200
250
h
450
500
550
600
h
p
hr
max
fine layers. The disadvantage of this method is that it's
h(nm)
submit to the influence of the operator and this influence
can affects the resolution power and analysis of the
FIGURE 1 - Schematic graphic of the measurement cycle
impression, increasing considerably the uncertainty
considering the force-indentation depth behaviour (Machado,
measurements.
2005).
31
Where A is the application of the test force; B is the
With the automation of the measure, this technique can
removal of the test force; C is the tangent to the curve B
provide the calculation of several important
at F ; F is the test force (mN); F is the maximum test
characteristics of the materials, among them (ISO
max
max
force (mN); h is the indentation depth under applied test
14577-1):
force (nm); h is the maximum indentation depth at F
·
Martens Hardness (HM): defined as the test force F,
max
max
(nm); h is the point of intersection of the tangent to the
divided by the contact surface area of the indenter A (h)
r
s
curve B at F with the indentation depth-axis (nm) and h
(up to 2001 it was called Universal Hardness), equation
max
p
is the permanent indentation depth after removal of the
2. It includes the plastic and elastic deformations of the
2
test force (nm).
material (N/mm ).
F
The figure 2 shows a cross section of one indentation
HM =
(2)
where is possible to identify the depths monitored during
A ( h)
s
the test.
·
Indentation Hardness (H ): defined as the maximum
IT
test force F , divided by the projected area of contact
max
(cross section) between the indenter and the sample
A (h ), equation 3. It includes the plastic deformation only
p
c
2
(N/mm ).
Fmax
H
= (3)
IT
A ( h )
p
c
·
Indentation Modulus (E ): defined from the slope of
IT
FIGURE 2 - Sketch of the cross section of one Vickers
2
the tangent of the force removal curve (N/mm ). It
impression, considering the measurement cycle with the
includes characteristics of the indenter and of the
force-indentation depth behaviour (ISO 14577-1).
sample. In the equation 4, v is the Poisson's ratio of the
a
sample; E is the reduced modulus of the indentation
r
Where p is the indenter tip; i is the surface of residual
contact; v is Poisson's ratio of the indenter and E is
p
p
plastic deformation in sample; S is the surface of sample
modulus of the indenter. In the equations
a
5 and 6, C is
s
at maximum indentation depth and maximum test force;
the compliance of the contact associated to the
h is the maximum indentation depth at F (mm); h is
indentation in the sample, that is the inverse of the
max
max
p
the permanent indentation depth after removal of the
contact stiffness S.
test force (mm) and h is the depth of the contact of the
c
indenter with the sample at F (mm).
2
max
1 n
-
a
E
=
IT
(4)
Comparing this method to the classic hardness
2
1
(
1 n
-
p
)
measurement (Brinell, Rockwell and Vickers) where the
-
size of the impression is measured only after the
E
E
r
p
removal of the total or additional test force, it was
noticed how much this new method was more powerful
p
E =
when one wanted to analyse material properties, mainly
r
(5)
2 C
A ( h
´
´
)
the localised measurements and small thickness of the
s
p
c
materials, remarkably in the micro and nanometer
1
dh
ranges.
C
=
=
(6)
s
S
dF
Only, in 1997 the technical subcommittee ISO/TC
164/SC 3 decided to work on this item and to develop an
Thus, the IIT has been turned important technique in the
International Standard based on the document “ISO/TR
development of nanostructural materials, thin films,
14577 Instrumented Indentation Test for Hardness and
ceramic materials, etc., for its speed and capacity to
other Materials Parameters” with the following parts:
determine these mechanical properties independently
“part 1 - Test method”, part 2 - Verification and
from hardness. This method is frequently the only one
calibration of testing machines” and part 3 - Calibration
which it makes possible the research of properties in tiny
of reference blocks. In 2001 it was decided to start a
areas of materials (< 200 nm), (Göeken and Kempf,
work in the “part 4 - Test method for coatings”.
2001).
From the effective beginning of the establishment of this
2.3. Field of Application
new method, called Instrumented Indentation Test (IIT)
to the current days, the technical possibilities of the test
The application fields of IIT are large and diversified,
force application, the measurements of indentation
besides to provide information for the hardness and the
depth, the registration and storage of data and the
elastic modulus, they also provide important information
graphic representations of the results, has being
on other properties of the materials. Among them, some
optimised to better understanding of the equipment,
of general and current importance in the scientific
mainly in the meaning of the automated control of its
research can be outstanding, such as (Hysitron Inc.,
functions, through a computer.
Minneapolis, MN, USA):
32
· Characterization of nanoscale components.
investigate the processing of materials, e. g., there is a
· Assess of adhesion of bond pads.
critical mass in the Country, although incipient, that is
· Quantification of wear resistance of wear-resistant
capable to caring out instrumented indentation tests with
coatings.
high quality, concentrating efforts to familiarize the
· Evaluation of interfacial toughness, mechanical
necessary language for interpretation and discussion of
properties of individual phases.
the results (Pintaúde and Machado, 2003).
· Measurement of viscoelastic properties of polymers.
· Quantification of static and dynamic mechanics of
MEMS and NEMS devices.
3.1. Brazilian demands
· Quantification of fracture toughness and interlayer
adhesion.
3.1.1. Nanostructural Materials
· Wear resistance and multi-layer adhesion of optic
cables.
The Department of Metallurgy and Materials
· Characterization of compatibility of proposed bio-
Engineering (DEMET) of the Federal University of Minas
replacement materials.
Gerais (UFMG) presents a high activity level in the field
of mechanical conformation of metallic materials, where
3. AN OVERVIEW OF THE BRAZILIAN
the need of determination of the final properties exists
NANOINDENTATION RESEARCH GROUPS
after processing that are quite heterogeneous, macro
and microscopically. Local hardness measures in
In Brazil, the first research groups that showed the
nanometer level are special for the evaluation of the
interest in the mechanical properties characterization in
deformation heterogeneity allowing studies on the
micro and nanometer levels where those linked to
consequences of this phenomenon. Nowadays is
applied physics area of the universities, remarkably
relevant the development of materials said
those from surfaces engineering area.
nanostructured with very small grain sizes, in the
nanometer range, what checks to the material a
In 1996 was created in the Physics Department of
mechanical resistance much larger than the alloys with
F e d e r a l U n i v e r s i t y o f P a r a n á - U F P R , t h e
conventional microstructure.
Nanomechanical Properties Laboratory with the
acquisition of the Nanoindenter II equipment (Nano
The methods of structural processing more adequate for
Instruments Inc., USA).
industrial applications are based on the Severe Plastic
Deformation (SPD). Among the techniques of SPD, the
Also in the middle of the nineties, the Surface
most promising are the Accumulative Roll Bonding
Phenomenon Laboratory of the Mechanical Engineering
(ARB) and the Equal Angular Channel Pressing (ECAP)"
Department from the São Paulo University USP-SP,
(Costa et al., 2005).
acquired an instrumented indentation test, the
Fischerscope H100V (Helmut-Fischer GmbH,
From these methods, very high rates of plastic
Germany).
deformation can be obtained through the accumulative
deformation after a convenient number of passes.
Later on, in 1998, the Group of Studies of Surfaces and
Interfaces Properties of the Physics Faculty of Catholic
In the figures 3a) and 3b) examples of deformations are
University of Rio Grande do Sul PUC-RS, also acquired
given by the process ARB in Interstitial Free (IF) steel.
an equipment Fischer H100V.
The understanding of the processes of structural
refinement that take to the formation of nanometer grains
In 2003, other two groups acquired equipment's of
size, requests detailed characterization of the
hardness using the instrumented indentation test
nanostructure of the material, what can just be carried
technique. A Hysitron Triboindenter (Hysitron Inc.,
out with advanced microscopy techniques, like the
USES) was acquired by the Plasma and Applications
A t o m i c F o r c e M i c r o s c o p e ( A F M ) , a n d t h e
Laboratory of Physics and Chemistry Department of the
measurements of nanomechanical properties
State University from São Paulo UNESP-Guaratinguetá,
throughout IIT, that seams to be the only available
and a Dynamic Ultra-micro Hardness Shimadzu DUH-
technique in the study of this structural evolution (Costa
W201S (Shimadzu Co., Japan) and a Hysitron
et al., 2005).
Triboscope were acquired by the Technological
Metallurgy Section of CETEC-MG. In 2005 was the
Laboratory of Tribological Coatings of the Metallurgy and
Materials Department of UMFG that acquire a Shimadzu
DUH-W201S, similar to the CETEC-MG machine.
Beyond of those research groups, the Tribology and
Materials Laboratory of the Physical Sciences
Department of the Federal University of Uberlândia-
UFU, comes developing in the own laboratory
instrumented indenter to determine properties in high
a) AFM images, scan size
= b) AFM images, scan size =
temperatures environments (Franco et al., 2001).
5m
mx5m
m, Z scale = 100nm
2m
mx2m
m, Z scale = 150nm
It's important to point out that these research groups
FIGURE 3 – IF steel: a) 2 passes ARB and b) 32 passes
come maintaining an interactivity with the groups that
ARB. (Costa et al., 2005)
33
3.1.2. Trybological films
The DEMET/UFMG has also been investing in the
research of surface engineering and, especially, in the
study of trybological coatings, because the demand for
measures in films with thickness more and more thin in
areas mechanically and chemically aggressive has
been increasing considerably.
The assessment of the substrate/coating performance
depends on the measurement of mechanical properties
of such deposited films as hardness, elastic modulus
and toughness. The conventional hardness test in the
micrometer range allows to determine some properties
of the films but, due to the small thickness, lower
application test forces are necessaries so that those
properties are measure without or with the minimal of
substrate influence and this is only possible from the
FIGURE 4 – AFM Images before and after the application of F
max
application of the technique of micro and nanohardness
= 100µN in gold films with high [a.1) and a.2)] and low [b.1) and
by IIT (Batista, 2001).
b.2)] porosity in an AISI 304 stainless steel.
3.1.3. Decorative films
Table 1 - Mechanical properties of gold interference films
electrodeposited on AISI 304 stainless steel.
Interference films deposition is an alternative for the
formation of colored protective layers on the surface of
Mechanical
High porosity film
Low porosity
stainless steel for decorative applications. The process
property
film
involves the growth of a chromium oxide films by
HIT (GPa)
2.4
6.9
electrochemical alternating current method on the
EIT (GPa)
75.2
101.5
surface of stainless steel checking to the films different
hmax (nm)
71.6
36.2
porosity depending on the duration of the current
Ap(hc) (nm2)
37276.1
14233.0
pulses.
In the figure 5 it is possible to observe that the residual
Results of researches in progress in the Technological
indentations of the film with high porosity are larger than
Foundation Center of Minas Gerais (Cetec/MG) for the
the indentation of the film with low porosity.
durability assessment of those colored stainless steels,
has been indicating that the morphology of the films can
increase the mechanical resistance of those materials.
The combination of IIT device in nanometer level with an
Atomic Force Microscope (AFM) allows indenting the
surface in very shallow depth and imaging the
impression with the same tip. Besides, this combination
enables to positioning the tip in very local area for
nanoindentation test with a high level of accuracy.
The figure 4 shows the topographic images of the gold
interference films deposited in an AISI 304 stainless
steel sheet with low and high porosity before and after
a.1) Before IIT.
a.2) After IIT.
the nanoindentation test with an IIT-AFM Hysitron
nanoindenter.
The mechanical properties extracted from the force-
displacement curves with F =100µN, applied over a
max
diamond indenter with triangular base (cube-corner),
figure 4, are presented in table 1.
b.1) Before IIT.
b.2) After IIT.
FIGURE 5 - Force-displacement curves for the high and low
porosity in gold interference films on AISI 304 stainless steel.
34
The combination of Nanoindentation test with an Atomic
Force Microscope is frequently the only method that
makes possible the characterization of near-surface of
nanomechanical properties of materials as small as
50nm. The possibility to have the indentation restricted
to a small fraction of coating thickness might be suitable
for isolating “coating-only” properties (Junqueira, et al.,
2005).
3.2. Other Demands
a) MgO {001}
b) Si {111}
3.2.1. Localized Measurements with Nanometer
Resolution
FIGURE 7 - TEM
images, F = 1mN.
max
The application of this new method can also be verified
in the work done by Kempf et al. (1998). It was carried
out studies in order to determine localized mechanical
properties with nanometer resolution of metallic alloys
to allow the best understanding of the materials with
objectives to the improvement of theirs structural
projects. It was used an nanoindenter equipment
coupled to a AFM with forces varying of nanonewtons to
micronewtons and they captured images with
amplifications of 300.000 times to study the matrix and
the precipitate ' of a
g
CMSX-6 superalloy, figure 6
(Machado, 2003).
FIGURE 8 - Fxh curves in MgO {001}and in Si {111},
F = 1mN.
max
4. CONCLUSIONS
As it can be noticed, the main technological
consequence in the difference of determination of the
FIGURA 6 - Impressions in the CMSX-6 alloy, F = 500mN. The
max
conventional hardness test with the hardness and other
matrix corresponds to the dark area and the precipitate ’ to the
g
property for instrumented indentation test is that, since
clear area.
the hardness measurement doesn't depend more on
the resolution of an equipment to analyse the produced
plastic impression, the hardness and other mechanical
3.2.2. Residual Dislocations Description and
properties can be measured in very small indentation
Elastic-plastic Responses
depths under application of test forces also in very small
scale. With the progress of technologies capable to
The nanoindentation behavior of various materials at
produce superficial modifications of the materials in
low test forces is also currently used to investigate, with
nanometer level (nanotechnology, nanoscience), the
the immediate goal, the determination of the initial
hardness and other mechanical properties, became
stages of material response to elastic-plastic contacts.
dependent of the test force applied and of
Results relating to the indentation behavior of {111}Si
measurements in very tiny area of the material surface.
and {001} MgO at force of 0,1mN to 5mN using a
Berkovich indenter is being researched. Plane-section
Because of that, the research centers and the
Transmission Electron Microscopy (TEM) observations
universities in Brazil are beginning to make efforts in the
are used to describe the residual dislocation structures
development of projects in the field of the
produced in MgO at test forces down to 0,1mN and to
nanomechanical materials characterisation, because
describe the elastic-plastic response (i.e., dislocations,
the nanotechnology and nanoscience areas are being
phase transformations and fracture) of silicon at test
shown as a strategic and important demand for the
forces down to 0,25mN. The TEM results, figures 7a) e
innovation in scientific and technological for the
7b), together with associated Atomic Force Microscopy
development of the nations, and the know-how of this of
(AFM) images of indentations and the indenter tip, are
the micro and nanoindentation technique comes to
directly related to the initiation of plastic deformation in
support these needs.
these materials and, more generally, to the elastic-
plastic response seen in acquired load-displacement
Acknowledgments: The authors, 2 and 3, thank CNPq
plots, figure 8 (Hockey, Machado and Guin, 2005).
and FAPEMIG for financial support.
35
5. REFERENCES
BATISTA, J. C. A. Promising duplex coatings for
MACHADO, R. R. Padronização da Micro e
tribological application at elevated temperatures. Belo
Nanodureza Por Penetração Instrumentada Belo
Horizonte: Escola de Engenharia da UFMG, 2001.
Horizonte: Escola de Engenharia da UFMG, 2005.
156p. (Tese, Doutorado em Engenharia Metalúrgica).
157p. (Tese, Doutorado em Engenharia Metalúrgica).
COSTA, A. L. M., CASTRO, A. L. R., MACHADO, R. R.,
PINTAÚDE, G., MACHADO, R. R. Ensaios de
VILELA, J. M. C., ANDRADE, M. S. Nanoestrutura e
Penetração Instrumentada como Ferramenta para a
propriedades mecânicas de aços Processados por
Caracterização de Ligas Tratadas Termicamente. In: I
severa deformação plástica. In: III ENCONTRO DO
CONFERÊNCIA BRASILEIRA SOBRE TEMAS DE
INSTITUTO DO MILÊNIO DE NANOCIÊNCIAS.
TRATAMENTO TÉRMICO. Indaiatuba, Brasil. Anais
Tiradentes, MG, 2004.
TTT 2003. 2003. v.1, p.292-302.
DIETER, G. E. Mechanical Metallurgy. SI Metric Edition.
POLZIN, T. Universal hardness - Working principle,
Singapure: McGraw Hill Book Company, 1988. 751p.
standardization, field of application. In: MATERIALS
TESTING 39, 1997, Berlin, Germany. Deutsches Institut
FISCHER-CRIPPS, A. C. Nanoindentation. 1.ed. Ann
für Normung, 1997. 7p.
Arbor: Springer-Verlag New York, Inc, 2002. 197p.
WILDE, H.R., WEHRSTEDT, A. Martens Hardness HM,
FRANCO, S. D.; SOARES, A. B.; PÉLIZER, M.C.
an international accepted designation for "Hardness
D e s e n v o l v i m e n t o e C o n s t r u ç ã o d e u m
under test force". In: DOCUMENT N 767 OF ISO/TC
Microesclerômetro / Microdurômetro Totalmente
164/SC3, 2000, Berlin, Germany. Deutsches Institut für
Informatizado para Altas Temperaturas. In: XVI
Normung, 2000. p.1/7-7/7.
Congresso Brasiliero de Engenharia Mecânica, 2001,
Uberlândia. Anais do XVI XVI Congresso Brasiliero de
Engenharia Mecânica, 2001. v. 3. p. 261-270.
Göken, M., Kempf, M. Pop-ins in Nanoindentations - the
Initial Yield Point, Z. Metallkunde 92, p.1061-1067,
2001.
Hockey B. J., Machado, R. R., Guin, J. P.
Nanoindentation Studies on Silicon and MgO, Journal of
Materials Research, 2005.
I N T E R N A T I O N A L O R G A N I Z A T I O N F O R
STANDARDIZATION, Geneva. ISO 14577-1 Metallic
materials - Instrumented indentation test for hardness
and materials parameters - Part 1: Test method.
Geneva, 2002. 25p.
JUNQUEIRA, R. M. R., ANDRADE, M. S., DE CASTRO,
A. L. R., MACHADO, R. R. A study of colored
interference films on ASTM 304 stainless steel through
a combination of instrumented indentation test-atomic
force microscopy In: III LATIN AMERICAN
SYMPOSIUM ON SCANNING PROBE MICROSCOPY.
Ouro Preto, Brasil, 2005. 2p.
Kempf, M., Göken, H., Vehoff, H. Nanohardness
measurements for studying mechanical properties of
metals, Applied Physics, v.A66, p.S843-S846, 1998.
LOW, S. R. Rockwell Hardness Measurement of
Metallic Materials. 1.ed. Gaithersburg, USA: NIST SP
960-5, 2001. 116p.
Machado, R. R. Propriedades mecânicas locais via
nanodureza, Metalurgia e Materiais, v.59 n.530, p.95-
96, 2003 (publicação autorizada: “M. Kempf, M. Göken,
H. Vehoff, Applied Physics A, v 66, p. 843-846, 1998”).
METALS HANDBOOK. Mechanical Testing. 9.ed, Ohio,
USA: ASM international, 1985. v.8.
36
THE NANOSCALE: THE SMALLEST NEW BIG DEAL IN MEASUREMENT
AT NRC
Co-written by National Research Council Canada scientists and writers
You'll never use this scale to measure anything at home
by. It's important that Canada is at the table—the
but it could one day be the measure of the tiny
countries that participate dictate what the standards will
technologies that transform our daily lives.
be.”
That's because a team of National Research Council of
“It's all about thinking one step ahead of the developing
Canada scientists is developing a measuring tool with
nanotechnology in order to facilitate commercialization,”
regularly spaced nanoscale lines or gratings much like
says Dr. Mark McDermott, a principal researcher at the
those on a ruler. It could be what many engineers reach
NRC National Institute for Nanotechnology (NRC-NINT)
for when building nanotechnologies. These length
and an Associate Professor in the Department of
standard artifacts will help guide Canada and the
Chemistry at the University of Alberta.
international community into a new age of minute
measurement.
NRC Scientists Measure the (Small) Force
The nanometre (billionth-of-a-meter) is the frontier of
industrial measurement. Scientists and engineers can
Imagine trying to glue pudding to Styrofoam. The
already create and manipulate nanoscale devices in their
inevitable result: a mess. It's what NRC scientists are
labs, and many computer chips have nanometre-level
working to avoid at the nanoscale. To do it, they're
detail. But there is a major missing ingredient in the
building one of the most sensitive small force detectors in
nanotechnology revolution—a measurement tool.
the world.
Scientists and engineers don't have an easily accessible
internationally recognized nanoscale length standard.
Small forces are those that at the molecular level
determine physical characteristics such as adhesion,
It's a situation reminiscent of the one that led to Canadian
hardness and elasticity. For large objects that we can
Sir Sanford Fleming's leadership in the creation of
see, we can readily measure these qualities. But at the
International Standard Time. The rise of transcontinental
nanometre (billionth-of-a-meter) level, it's a new world of
railroads in the 19th century necessitated standardized
material properties.
time in order to make the trains commercially reliable and
effective.
“When you start piecing together nanomaterials, their
small force characteristics determine whether you're
“We need to establish traceable and verifiable
going to succeed or fail,” says Dr. Mark McDermott, a
m e a s u r e m e n t s t a n d a r d s a n d m e t h o d s f o r
principal researcher at the NRC National Institute for
nanotechnologies,” says Dr. Jennifer Decker, team
Nanotechnology (NINT) and an Associate Professor in
leader for metrology for nanotechnology at the NRC
the Department of Chemistry at the University of Alberta.
Institute for National Measurement Standards (NRC-
“In the emerging field of commercial nanotechnology, it's
INMS). Dr. Decker is also a participant in the Canadian
critical to be able to measure and characterize these
Advisory Committee to the International Standards
small forces.”
Organization (ISO) Technical Committee on
Nanotechnologies, in particular the Working Group
Dr. McDermott is leading a collaborative NRC effort to
meetings to determine nanoscale metrology standards
create one of the world's most sensitive small force
and characterization.
measurement devices. Called an Interfacial Force
Microscope (IFM) it will function as an incredibly fine
“These standards will have a significant commercial
needle that pokes a nanomaterial and records how deep
impact since they'll set the rules that everyone will play
37
the needle goes (nanoindentation). This will provide
detailed measurements of a material's small force
characteristics, and thus how it will behave in relation to
other materials.
The research is a core part of an NRC cross-institute
project, led in Canada by NRC-INMS, to develop
q u a n t i f i a b l e m e a s u r e m e n t s t a n d a r d s f o r
nanotechnology.
The IFM project is in collaboration with University of
Western Ontario Professor Peter Norton. He's world-
renowned for his work in using IFM in nanotribology to
study the nanocharacteristics of interacting surfaces,
such as gears, in motion. The NRC-NINT team includes
Dr. David Munoz-Paniagua, a former Ph.D. student of Dr.
Norton's, and one of the only people in the world with
experience in IFM construction.
of the reflected beam is measured, and the value of the
average pitch is calculated. The NRC diffractometer
calibrates the average line spacing with an uncertainty
“At this level a small difference in length can make a big
much less than the distance between atoms.
difference in function. So if materials need to be
separated by two nanometres to work, and at 2.1
Another key tool is the metrological atomic force
nanometres the device doesn't function, you need to be
microscope currently being developed at NRC-INMS by
able to measure and control at that level.”
Dr. Brian Eves. Most scanning probe microscopes rely
upon calibrated artifacts such as the NRC length
The Canadian nanoscale length standard is being
standard chip to ensure they correctly measure length.
developed through a NRC cross-institute initiative
The metrological atomic force microscope will guarantee
involving four NRC institutes and two universities.
the correct measured length by using the definition of the
Together they have the unique mix of skills and abilities in
metre, based upon the speed of light in a vacuum, as its
nanoscale fabrication, instrument design, and metrology.
standard. One of its tasks will be to calibrate line spacings
smaller than currently possible with the imaging
As envisioned, each measurement standard, (imagine a
diffractometer.
patch of regularly-spaced lines), will be approximately
one square millimetre in size—eight of these grating
Science is such that there will in all likelihood be another
patches will be fabricated on a silicon chip about one
generation of nanoscale standards built perhaps on
centimetre square. So this length standard chip contains
intrinsic standards such as the inter-atomic spacing of
eight gratings ranging in nominal pitch from 150 nm to 10
crystalline silicon. Dr. Marek Malac at NRC-NINT will be
µm.
investigating the use of such standards using a
transmission electron microscope.
The prototype will be made at the recently established
Canadian Photonics Fabrication Center (CPFC), part of
For now, we need to answer the needs of scientists like
the Ottawa-based NRC-Institute for Microstructural
Dr. Linda Johnston at the Steacie Institute for Molecular
Sciences.
Sciences. Scanning probe microscopes and integrated
NRC-IMS scientists use electron beam lithography,
optical-atomic force microscopes are among the most
which utilizes a precisely controlled beam of electrons to
important tools for the development of nanotechnology.
pattern nanophotonic and nanoelectronic devices. This
The best instruments enable researchers to image living
expertise in creating nanoscale devices is being
cells and even the atomic structure of surfaces. For these
extended by the CPFC that is developing nanoimprint
microscopes to obtain accurate results it is necessary to
lithography to create a length standard prototype chip.
calibrate them frequently using one-dimensional grating
Led by researcher Dr. Frank Shepherd, the group will first
pitch standards. Dr. Shan Zou, NRC-SIMS, will also be
use electron beam lithography to make a template, or
working with NRC-INMS to develop artifacts for standard
master, in quartz. This template will be then be used to
force and distance measurements on soft biological
replicate exact copies of these nanometer grating length
samples.
standards.
And with our eye on the economy, and in particular the
One of the goals of the NRC Metrology for
support of trade and global manufacturing, the grating
Nanotechnology Program is to determine the extent to
artifacts will be used to support international comparison
which the gratings made by the nano-imprint lithography
experiments. If the pitch value of the artifacts fabricated
technique have the same line spacing. Metrologists in
by nanoimprint lithography can be shown to be
the dimensional metrology laboratory at NRC-INMS will
essentially identical, then multiple artifacts can be sent
do the determination.
simultaneously to National Measurement Institutes
around the world, improving the metrological integrity of
In the metrology laboratories, an imaging diffractometer
the comparison exercises—and giving scientists and
was developed to calibrate one-dimensional grating pitch
engineers that all-important easily accessible
standards: laser light is directed on the grating, the angle
internationally recognized nanoscale length standard.
38
ESTABLISHMENT OF THE SIM TIME SCALE
.
a
a
b
J. M. López-Romero, N. Díaz-Muñoz, M. A. Lombardi
aCentro Nacional de Metrología
km 4,5 Carretera a Los Cués, 76246, Querétaro, México.
mauricio.lopez@cenam.mx
b National Institute of Standards and Technology
325 Broadway, Boulder, CO 80305-3328, Estados Unidos de América.
ABSTRACT
The SIM time and frequency metrology working group has developed a comparison network for the Americas, with the goals of
improving metrology in the SIM region and to allow as many countries as possible to participate in the network. As of May
2008, ten National Metrology Institutes (NMIs) were participating, and six additional NMIs are expected to join the network by
the end of 2009. This paper describes how measurements from the SIM network will be used to generate a time scale named
SIM-time to be used as the time reference for the SIM region.
1. INTRODUCTION
participating in the SIM network with respect to the SIM
time scale will be available in real-time through the
The Sistema Interamericano de Metrología (SIM)
network itself.
consists of the National Metrology Institutes (NMI's)
located in the 34 states that are members of the
This paper presents the algorithm that will be employed
Organization of American States (OAS). Currently,
in the generation of the SIM-time scale, and also
about one half of the countries that are members of the
presents preliminary results obtained by the Centro
OAS operate and maintain a time and frequency
Nacional de Metrología, CENAM, where the time scale
metrology laboratory, and some of the remaining
algorithm is implemented on four Cs clocks and one
countries plan to establish a laboratory in the future.
active hydrogen maser. Much of the basic analysis
With the goal of developing an efficient comparison
presented in Section 2 is presented in detail elsewhere
mechanism throughout the Americas for time and
[3-5], but is summarized here for completeness.
frequency metrology, the SIM time and frequency
metrology working group has built a regional
2. ALGORITHM OF THE SIM-TIME SCALE
comparison network that uses the GPS common view
technique. The SIM time and frequency comparison
If a set of N atomic clocks is available, then an Atomic
network is helping to improve the development of
Time scale TA can be defined by the Eq. (1):
metrology in SIM region by promoting the participation
of as many countries as possible, and allowing each
N
1
country to see their comparison results in real time. The
TA (t)
å
=h (t) ,
(1)
i
time and frequency (TF) comparison network of SIM
N i=
1
began operations in 2005 with the participation of three
national laboratories: National Research Council (NRC)
where h (t) is the reading of the clock i at the time t. It is
i
of Canada, National Institute of Standards and
important to notice that in Eq. (1) every participating
Technology (NIST) of the United States of America and
clock has the same weight. If different weights are
the Centro Nacional de Metrología (CENAM) of Mexico
assigned to each clock, then the time scale TA is defined
1. As of May 2008, ten countries of the region were
as:
taking part in the comparison network, and 16 SIM NMIs
are expected to participate by the end of 2009. A report
N
1
with the most recent results of the SIM TF comparison
TA(t)
å
= h (t)
w
,
(2)
i
i
network was presented in [2].
N i=
1
To make efficient use of the comparison results
where
is the weight
w
of the clock i and the condition of
produced by the SIM TF network and to reinforce the
i
normalized weights is given by:
continuing development of metrology in the SIM region,
a SIM time scale, called SIM-time, will be generated.
The SIM-time scale will provide a time reference for the
N
SIM region that is as stable and accurate as possible.
1.
=
å
w
(3)
i
The comparison results of each of the NMIs time scales
i 1
=
1 This paper is reproduced from the Proceedings of the Simposio de Metrologia 2008, CENAM, México, with permission of its authors and the
Simposio's organizers.
39
It is possible to define each weight as constant
w
in time.
Once the time differences x
i
ki(t) are known
, it is t hen
However, the best scenario is given when a dynamic
possible to compute the time s cale TA by using Eq. (7).
weighting approach is implemented, that increases or
However, it is important to notice that this computes the
decreases the weight given to a clock according to its
time scale using a
post-processing scheme. In cases
frequency stability characteristics, which can change
where it is necessary to generate a time scale TA in real
over time for different reasons. In this case the weights
time, we must introduce a scheme of prediction for the
can be defined as inversely proportional to the
time differences among clocks and the time scale TA.
frequency stability of the clock under consideration,
where the frequency stability is measured in terms of the
One of the simplest models to predict the time difference
Allan deviation. In this scheme we can define the
of a clock with respect to a reference (we assum e the
weights as:
reference is more stable and accurate than the clock
1
(t)
w
µ
,
(4)
under consideration) is
:
i
( )
t
s
i
é
Dk ù
t
where
( ) is the
t
s
Allan deviation of the clock i for an
ˆx (t
)
t
x (t)
y (t)
+
=
+
+
...
+
t , (9)
i
k
k
ê
k
ú
integration time . The proportional constant is
ë
2 û
defined by the normalization condition on weights,
Eq. (3). In this way, the TA time scale definition in
where ˆx (t
)
t
+
is the prediction of the time difference
k
terms of the dynamic weighting takes the following
of clock k
respect to the reference for the future time
form:
t
t
+
. x (t )
k
is the (known) time difference between
N
N
1
h t
( )
w
h (t)
the clock k and the reference, and y (t )
i i
å
å
i
( )
t
s
k
is the fractional
i =
1
i =
TA(t) =
=
1
i
frequency difference at the time
t. Finally, D
is a
N
N
.
(5)
1
k
w
i
å
å
y (t
( )
t
s
constant accounting for changes of
) during the
k
i =
1
i =
1
i
interval.
Unfortunately, Eq. (5) cannot be implemented
experimentally as written, because the readings from
Eq. (9) can be seen as expansion of the x in terms of a
k
clocks h (t) are not observables. Experimentally it is
i
possible to know only the time difference between pairs
Taylor series around the value x (t ) for a time interval
k
of clocks.
of t
. Once the time difference x (t) is known through
k
We can rewrite Eq. (5) in terms of the time differences
Eq. (7), it is possible to predict the time scale TA for the
between participating clocks, by subtracting from each
time t
t
+
using Eq. (9). Here it is important to note that
side of the equation the reading of clock k at the time t as
the weighted average of the predictions ˆx (t
)
t
+
is not
k
follows:
necessarily zero; that is,
N
N
N
x (t) =
w
x (t) =
w
w
N
k
k
k å
å
å
i
ki
k 1
=
k 1
=i 1
=
ˆx (t
)
0.
¹
+
t
w
. (6)
å
(10)
k
k
N
k 1
=
x (t)
w
w
.
0
=
å
k
i
ki
k ,i 1
=
Once the (future) time t
is reached, it is possible to
know the time differences between participating clocks ,
If we define
x ( t ) as the time difference between clock
k
and then it is possible to compute the value of the time
k and the time scale TA at the time t, and define x as the
ki
scale TA for that time t
t
+
. Of course, the predict ed
difference between clock k and clock i and we take in
value of the time scale TA computed at time t for the time
consideration the normalization condition on the
t t
+
will not necessarily be equal to the computation of
weights in Eq. (3), then Eq. (6) takes the form:
TA at time t
t
+
. Under th is scheme , the time scale
N
prediction for t
t
+
can be corrected by the
time
x (t) =x (t .
)
w
(7)
k
å
i
ki
difference measurements by using:
i 1
=
This last equation defines the time scale TA in terms of
N
the time differences between participating clocks. It is
x (t
)
t
x t
x
t
w
t t(11)
k
j [
=
+
ˆ (
)
(
)
å
j
jk
]
.
+
-
+
important to notice that the weighted average of x (t)
k
j 1
=
is zero, because x (t)= - x (t); that is,
kj
jk
N
N
N
The prediction
ˆy (t
)
t
+
of the fractional frequency
i
x (t) =
w
x (t) =
w
w
k
k
k å
å
å
i
ki
deviation of clock i for time t
t
+
is made according to:
k 1
=
k 1
= i 1
=
(8)
N
ˆ
x (t
)
t
x (t)
-
+
k
k
x (t)
w
w
0.
=
å
ˆy (t
)
t
=
+
.
(12)
k
k
i
ki
t
k ,i 1
=
40
Once the (future) time
t
is reached, the
Fig. 1 presents a schematic of the time difference
correction for the frequency prediction can be made
measurement system (the phase comparator). The
through the exponential filtering defined by
clocks are compared through their 5 MHz output
signals. The phase comparator measures the time
1
differences between clocks modulo one signal period
y (t
)
t
=
+
t t
+
+
,
(200 ns). To obtain the total phase difference it is
i
[
ˆy (t
)
m ( ) y (t)
i
i
i
]
(13)
1
m
+
necessary to post-process the phase comparator
i
results.
where mi is given by the Eq. (14) as:
To transform the time scale TA from a virtual time scale
é
2
ù
1
1
4 t
(with no physical signal defining the time scale) to a real
m ( )
t ê
=+
min,i
ú
-
1
,
i
(14)
2
2
time scale (with a physical signal defining the time scale)
ê
3
3 t ú
ë
û
we use a micro phase stepper (MPS). The MPS steers
the 5 MHz frequency signal of the active hydrogen
maser so that it follows the virtual TA time scale.
and t
min,i is the integration time at which the noise
floor of the clock i is reached.
The output of the MPS is used to measure the time
difference between the time scale and the corrected
frequency of the hydrogen maser. The MPS is controlled
by an automatic servo loop so that the time difference
3. RESULTS
between the TA and the MPS output remains constant
(Fig. 2).
The algorithm presented in the previous section has
been implemented at CENAM on four Cs clocks and one
active hydrogen maser. The time scale TA is computed
every hour with the dynamic weighting algorithm
described in [4]. The system that measures the time
Ch. N+1
differences between clocks, also referred to as the
Ch. N
Ch. 3
phase comparator, utilizes the dual mixer frequency
Ch. 2
technique and has a resolution of 20 ps. The phase
Ch. 1
comparator has 32 input channels, which allows it to
MPS
compare that same number of clocks. It performs one
Master
Clock 1
.
time difference measurement every second for each of
Clockj 2 Clock 3
.
Máser
clock
w
the 32 channels in use. One Cs clock (labeled as Cs I) is
w2
3
w
w
w1
N
0
selected as the master clock, and all of the other clocks
w=0
are compared to the master.
In this section we show the results obtained at CENAM
TA
during the implementation of the time scale algorithm.
The results were obtained from six weeks of continuous
Fig. 2. Schematic showing how the output of the micro phase
time scale generation (from April 5 to May 16, 2008).
stepper is held in agreement with the time scale TA.
The following results are considered as preliminary
because it is necessary to measure the performance of
the time scale algorithm for a longer period to obtain
Fig. 3 shows the measurement results from the phase
more confidence in the results.
comparator during six weeks, from April 4th to May 16th,
2008. The vertical axis corresponds to the time
difference of participating clocks with respect to Cs I, the
x
(t)
h (t) h (t)
-
=
master clock. Discontinuities observed at 0 ns and 200
N 0
0
N
x (t)
h (t) h (t)
-
=
30
0
3
ns are due to the fact that the phase comparator
performs time difference measurements modulo one
period of the 5 MHz signals (200 ns). To correct for these
discontinuities, it is necessary to post-process the
Ch. N
phase comparator measurements. It is also important to
Ch. 3
Ch. 2
notice the frequency change of clock J on April 12th,
Ch. 1
2008, marked in the figure within a circle.
Master
Clock 1
Clock 2
Clock 3
Clock N
clock
x ( )
t
h ( )
t
h (t) [
h (t)
h (t ]
)
h t
h t
-
-
-
=
-
=
ij
j
i
0
i
[
( )
(
0
j
]
)
Fig. 1. Schematic of the time difference measurement
system used at CENAM, also referred to as a phase
Fig. 3. Time difference measurement of participating clocks
comparator. The system performs one measurement every
with respect to the master clock (Cs I). The black line
second.
corresponds to the MPS output.
41
Fig. 4 shows the time differences of the participating
4. DISCUSSION
clocks with respect to the time scale TA. It is interesting
th
to note how the frequency change of clock J on April 12 ,
Here we first present a discussion of the obtained
2008 affected the time scale TA performance.
results when the Cs clock is used as the master clock.
Then, we will discuss results when the time scale TA is
used as the master clock.
4.1. Measurement Results when Cs I is Used as the
Master Clock (Fig. 5)
Due to the high frequency stability of the active
hydrogen maser in the short term, the relative frequency
stability between Cs I and the maser is a measure of the
frequency stability of the master clock Cs I, which is
about 8 1014 at 1 hour. If the Cs I clock is compared to
another reference more stable than the maser, we will
expect no significant change in this number, because it
is already limited fundamentally by the Cs I clock itself. A
Fig. 4 Time difference of participating clocks with respect to
similar argument can be applied to the results for the
the time scale TA.
stability measurement of clock H, because clocks Cs I
and Cs H have the same manufacturer's specifications
for stability and perform similarly when they are
measured in the laboratory. According to the
manufacturer's specifications, Cs I and Cs H should
have frequency stability around 7 10-14 for an average
time of 1 hour, which is in close agreement with our
results shown in Fig. 5.
Both Cs J and Cs G are less stable than Cs I and Cs H.
This was expected, because both of them are low
performance clocks. It is also interesting to note that the
frequency correction on clock Cs J has an effect on the
frequency stability results in the long term.
For integration time around one day or longer, note that
the frequency stability of Cs H approaches the stability
Fig. 5 Frequency stability of the time difference of
of the maser and MPS. It is actually because the
participating clocks with respect to the master clock (Cs I).
frequency stability of the maser approaches the
The black line corresponds to the frequency stability of the
performance of a Cs clock. Finally, the frequency
MPS output.
stabilities of clocks Cs J and Cs G are interesting for the
purpose of evaluating the time scale performance. The
Figs. 5 and 6 show the frequency stability of the
frequency stability of these two clocks agrees with the
comparisons shown earlier in Figs. 2 and 3.
manufacturer's specification for low performance Cs
clocks. Because of their relatively large instabilities, if
these two clocks are compared with a reference more
stable than the Cs I clock, like the time scale TA, we will
expect no significant changes in the frequency stability
results.
4.2. Measurement Results when the Time Scale TA is
Used as the Master Clock (Fig. 6)
As we discussed in the previous section, the frequency
stability results for Cs J and Cs G are similar to the
results when those clocks were compared with respect
to Cs I.
The frequency stability for Cs I clock is slightly better
than when it was compared with the maser. For
integration time of 1 h the stability of Cs I when it was
compared to the maser was about 8 10-14, as opposed
to about 7 10-14 when compared to the time scale. This
Fig. 6. Frequency stability of participating clocks with respect
slight difference indicates that the stability numbers are
to the time scale TA.
limited by the (absolute) frequency stability of Cs I, and
that the time scale is more stable than the maser itself. A
similar discussion also applies to the Cs H clock.
42
The difference in stability between the maser and the
REFERENCES
MPS is due to the corrections of the maser frequency
made by the MPS. The MPS corrects the maser
[1] M. A. Lombardi, A. N. Novick, J. M. Lopez, J. S.
frequency once per hour if necessary, causing a small
Boulanger, and R. Pelletier, “The Interamerican
perturbation on the maser frequency stability, as we can
Metrology System (SIM) Common-View GPS
see in Fig. 6. These results suggest that corrections to
Comparison Network” Proceedings of the Joint
the maser frequency output can be made less often than
2005 IEEE Frequency Control Symposium and
once per hour, perhaps once per day, and that the
Precise Time and Time Interval (PTTI) Systems and
magnitude of the corrections can be made smaller.
Applications Meeting, August 2005, pp. 691-698.
These possibilities will be carefully analyzed during the
coming months.
[2] J. M. Lopez R., M. A. Lombardi, A. N. Novick, J.-S.
Boulanger, R. de Carvalho, R. Solis, and F.
The results of the TA time scale performance are
Jimenez, “The SIM Network: Improved Time
satisfactory. The TA time scale appears to be more
Coordination for North, Central, and South
stable than the clocks participating on its generation.
America”, European Frequency and Time Forum
However, the stability of the time scale can probably be
(EFTF) 2008, 23 – 25 April, Toulouse, France.
improved by optimizing the method used to apply
frequency corrections to the maser output.
[3] Guinot B., “Some properties of algorithms for
atomic time scales”, Metrologia, 1987, 24, pp. 195-
During the implementation stage of the SIM time scale
198.
with real data from the SIM TF comparison system will
be necessary to take into account some important
[4] An interesting discussion of the properties of the
aspects, such as noise from the comparison system. To
AT1 and ALGOS algorithms can be found in:
face that inconvenient we estimate the necessity to use
P. Tavella and C. Thomas, “Comparative study of
of a previous filtering scheme on the measurement data
Time Scale Algorithms”, Metrologia 1991, 28, pp.
before applying the algorithm here discussed. We
57-63.
estimate that about 30 Cs clocks and about 10
Hydrogen masers will contribute to the SIM time scale.
[5] M. Weiss and T. Weisser, “AT2, A New Time Scale
Many of the individual clock signals are combined into a
Algorithm: AT1 plus Frequency variance”,
single time scale that is measured by the SIM network.
Metrologia 1991, 28, pp. 65-74.
For example, there are four Cs clocks and six Hydrogen
Masers involved in the generation of UTC(NIST).
Because the SIM network compares UTC(NIST) and
not the individual clocks behind it, the weight of time
scales like UTC(NIST) will be larger than the weight of
signals currently supported by a single clock like
UTC(ICE) in Costa Rica.
5. CONCLUSIONS
The Centro Nacional de Metrologia, CENAM, has
developed and implemented an algorithm similar to the
NIST AT1 algorithm 4 with the goal of providing a time
scale for the SIM region, called SIM-time. The SIM-time
scale will be generated using the algorithm discussed
here; utilizing the time difference measurements
provided by the SIM time and frequency network that is
already in operation. The preliminary results obtained
by implementing the SIM-time algorithm at CENAM on
four Cs clocks and one active hydrogen maser are
satisfactory. Special attention has been taken to
implement the algorithm with the robustness required
when generating a high performance time scale.
Software is currently being added to the SIM time and
frequency network that will feed the time scale algorithm
with the necessary time difference data. We expect to
generate the SIM-time scale by the end of 2008, and to
make the results available in near real-time through the
SIM time and frequency network.
43
rono
C BREVE RESEÑA DE LOS ORÍGENES DEL SIM
Anselmo Manuel Araolaza-Rodríguez
.
Centro Nacional de Metrología de Panamá
Durante la gestión del Sr. Roberto Monti dentro del
The idea of building up a Sistema Interamericano de
Programa Regional de Desarrollo Científico y
Metrología-SIM came up in 1974 during the
Tecnológico de la OEA, estando en marcha el Proyecto
administration of Mr. Roberto Monti within the OAS
Especial “Sistema Regional de Metrología y
Regional Program for Scientific and Technology
Calibración”, en 1974 se gesta la idea de constituir el
Development framework, when the special project on
Sistema Interamericano de Metrología-SIM.
"Sistema Regional de Metrología y Calibración" was
running.
En la Reunión de Coordinación Especial de Metrología
y Seminario de la OEA, celebrado en Panamá y
During the OAS meeting about Special Coordination on
organizada por la Directora de la Comisión Panameña
Metrology and Seminar, held on Panama organized by
de Normas Industriales y Técnicas, COPANIT, Ing.
the Director of the Panama Commission for Normas
Maricela Ferrer, del 25 al 30 de septiembre de 1977, se
Industrial and Technical Standards, COPANIT, Eng.
redacta la Resolución No. 1, que decía:
Maricela Ferrer, on September 25 to 30, 1977, a
Resolution No. 1 was issued, to read:
“Considerando: la resolución formulada por el CIECC
de Mar del Plata (CIECC 174/72) referente a la
Considering: the resolution issued by the CIECC in mar
implantación de un sistema regional de metrología y
del Plata (CIECC 174/72) relative to the implementation
calibración, los acuerdos de las reuniones de Boulder
of a regional system of metrology and calibration, the
(NBS, noviembre de 1974) y Buenos Aires (INTI, agosto
agreements of Boulder (NBS, November 1974) and
de 1975); y considerando que las posibilidades que ya
Buenos Aires (INTI, August 1975); and considering the
ha abierto el desarrollo aún en curso del Proyecto
opportunities brought by the already started Special
Especial originado en aquella resolución y vista la
Project derived from such a resolution, and due to the
imperiosa necesidad de asegurar la coordinación de los
imperilous need to ensure the coordination of the efforts
esfuerzos realizados y por realizar; los participantes
done and to be done; the participants submit to the OAS
solicitan a la OEA y a los respectivos gobiernos, la
and the conforming governments the following
consideración de la siguiente PROPUESTA: El
PROPOSAL: The establishment on a permanent basis
establecimiento con carácter permanente del Sistema
of the Sistema Interamericano de Metrología (SIM),
Interamericano de Metrología (SIM) de conformidad
according to the following:
con las bases siguientes:
To promote the international cooperation among the
Promover la cooperación internacional entre los
involved organisms of the participant countries, aimed
organismos competentes de los países participantes
to contribute to the perfecting of the activities on Legal,
para contribuir al perfeccionamiento de las actividades
Industrial and Scientific Metrology. In order to achieve
en las áreas de la Metrología Legal, Industrial y
that, actions will be taken directed to reach:
Científica. A tal efecto, las acciones a realizar tenderán
a lograr:
1. The definition of National Measurement Systems in
every country.
1.
La definición del Sistema Nacional de Mediciones
2. The establishment of a hierarchy of measurement
de cada país.
standards in each country and its link to the
2.
El establecimiento de la línea jerárquica de
international measurement standards.
patrones en cada país y su enlace con los patrones
3. The compatibility of the results of the measurement
internacionales.
processes produced by the laboratories participating
3.
La compatibilidad de los resultados de los procesos
in the system.
de medición correspondientes efectuados en los
4. The formation of technical and scientific personnel.
laboratorios del Sistema.
5. The acquiring and distribution of technical and
4.
La formación de personal técnico y científico.
scientific documents.
5.
La obtención y distribución de los documentos
6. The link to the General Conference on Weights and
técnicos y científicos.
Mesures (CGPM), the International Organization for
6.
La vinculación con la Conferencia General de
Legal Metrology (OIML) and other relevant national
Pesas y Medidas (CGPM), la Organización
and international organizations.
Internacional de Metrología Legal (OIML) y otros
organismos nacionales e internacionales
Besides, voluntary participation as members of the SIM
especializados en la materia.
could be done through the corresponding national
organizations for metrology.
44
Además serán Miembros del SIM los países que
Finally, the SIM is formally constituted in the meeting
voluntariamente participen a través de sus órganos
held on Buenos Aires, under the sponsorship of the
nacionales de metrología".
OAS, during the administration of Marcelo Alonso,
Director of the Department of Scientific Issues,
Finalmente el SIM se constituye formalmente en la
organized by the INTI on September 4 to 6, 1979, with
Reunión celebrada en Buenos Aires, con patrocinio de la
the attendance of representatives of the metrological
OEA durante la gestión de Marcelo Alonso, Director del
organizations of Colombia, Chile, Mexico, Guatemala,
Departamento de Asuntos Científicos y organizada por
Venezuela, Bolivia, Costa Rica, Brazil, Argentina,
el INTI, del 4 al 6 de septiembre de 1979, con
Paraguay, Peru, Uruguay and Panama.
participación de representantes de las entidades
Metrológicas de Colombia, Chile, México, Guatemala,
The first Coordinating Committee was composed by:
Venezuela, Bolivia, Costa Rica, Brasil, Argentina,
Paraguay, Perú, Uruguay y Panamá.
President: Prof. Rafael Steinberg, Argentina.
El Primer Comité Coordinador fue integrado por:
Secretary: Dr, Armenio Lobo Da Cunha Filho, Brazil
Presidente: Prof. Rafael Steinberg, por Argentina.
Vocales:
Dr. Héctor Nava Jaimes, Mexico
Eng. Esmeralda Hernández, Panamá
Secretario: Dr, Armenio Lobo Da Cunha Filho, por Brasil
Eng. Ramón de Colubi, Venezuela.
Vocales:
Dr. Héctor Nava Jaimes, por México
Ing. Esmeralda Hernández, por Panamá
Ing. Ramón de Colubi, por Venezuela.
La foto muestra, de izquierda a derecha, a: Ing. De
In the picture, from left to right: Eng. De Colubi, Dr. Lobo
Colubi, Dr. Lobo Da Cunha Filho, Prof. Steinberg, Dr.
Da Cunha Filho, Prof. Steinberg, Dr. Nava Jaimes and
Nava Jaimes e Ing. Hernández.
Eng. Hernández.
En otra reunión de coordinación del SIM, celebrada en
In other coordination meeting of SIM, held at INTI,
el INTI, Argentina, el representante del National Bureau
Argentina, Dr. Goldman, as representative of the
of Standards, NBS, hoy National Institute of Standards
National Bureau of Standards, NBS, now National
and Technologies, NIST, Dr. Goldman, manifestó que
Institute of Standards and Technologies, NIST, stated
por expresa decisión del gobierno de los EEUU de
that by a decision of the government of the USA the NBS
Norteamérica el NBS no iba a participar en el SIM como
was not going to become a SIM member, but that there
Miembro asociado, aunque sí dijo que en el NBS
was any intention to provide training in its metrology
estaban anuentes a recibir becarios para su
laboratories, as well as to provide experts to the
capacitación en los laboratorios de metrología, como
laboratories of the members, under the funding of the
así también enviar expertos a los laboratorios de los
SIM.
países miembros, con cargo a los fondos del SIM.
Given this latter situation, it came up the idea to
Ante esta situación de no participación de los EEUU de
transform the SIM into a "Sistema Iberoamericano de
NA dentro del SIM, surgió la idea de transformar el SIM
Metrología", to include Spain and Portugal, since
en el "Sistema Iberoamericano de Metrología", con
voluntary membership was permitted within the agreed
inclusión de España y Portugal, en virtud que dentro de
objectives for the SIM.
los objetivos establecidos en el SIM, podrían participar
45
también otros países: "Además serán Miembros del
Dr, Manuel Cadarso, participant as observer for Spain,
SIM los países que voluntariamente participen a través
was a great promoter of this idea.
de sus órganos nacionales de metrología". (sic)
In 1982, Dr. Cadarso proposed to create a Metrology
El Dr. Manuel Cadarso, quien participó como
Center in Spain, and in March 1989 the Centro Español
observador español, fue un gran impulsor de esa idea.
de Metrología, CEM, started operations being the King
En 1982 el Dr. Cadarso propuso crear un Centro de
of Spain Don Juan Carlos I present and so was the
Metrología en España y en marzo de 1989 se inaugura
Queen Doña Sofía. It is highlighted that Dr. Cadarso and
el Centro Español de Metrología, CEM, con presencia
the King were arm-comrades so it was not difficult for the
de los Reyes de España Don Juan Carlos I y Doña
King to become sympathetic with the idea and support
Sofía. Cabe señalar que el Dr. Cadarso era compañero
the initiative.
de armas del Rey, quien hizo suya la idea de crear un
The new idea about the SIM also was very well received
Centro de Metrología en España y apoyó firmemente la
in the PTB, Germany, since this regional supra-structure
iniciativa.
was going to facilitate the provision of resources as
equipment, experts and scholarships into Latin
La idea de un nuevo SIM, también fue bien vista por el
America. Thus, the German technical cooperation could
PTB de Alemania, ya que entonces una estructura
be forwarded through the CEM
supra-regional le serviría para canalizar la importante
ayuda en equipamiento, expertos y becas que ofrecía, y
This supra-structure could not be completed since Dr.
ofrece, Alemania a América Latina. Así, a través del
Cadarso passed away by a cardiac disease and also
CEM se hubiera podido coordinar la cooperación
because the representative from Ecuador had not
técnica alemana, dentro de una nueva estructura del
agreed with an Iberoamerican system that, he said, was
SIM.
closing out the future participation of USA.
Esta nueva estructura supra-regional no se pudo
After some years, the USA position changed and the
concretar, ya que el Dr. Cadarso falleció
SIM got revitalized, with the inclusion of Canada and
prematuramente por una dolencia cardiovascular y
other Caribbean countries as well.
también porque dentro del SIM, el representante del
Ecuador no estaba de acuerdo con un sistema
But that deserves another story.
iberoamericano, ya que decía que eso cerraba las
puertas a una participación futura de los EEUU de Norte
América.
Después de varios años, cambió la postura oficial de
EEUU de Norte América y a través del actual NIST se
revitalizó el SIM, con la incorporación también de
Canadá y otros países del Caribe, conformando la
estructura actual del SIM.
Pero esto merece otra historia.
46
NOTI-SIM
Noticias en el SIM
SIM News
3rd. Tri-national Workshop on Standards for
3rd. Tri-national Workshop on Standards for
Nanotechnologies
Nanotechnologies
Llevado a cabo en las instalaciones del CENAM,
Held on February 12, 2009, in CENAM facilities in
Querétaro, México, el 12 de febrero de 2009, con la
Queretaro, Mexico, actually became a tetra-national
participación de 18 conferencistas de Brasil, Canadá,
workshop with the participation of 18 lecturers from Brazil,
Estados Unidos de América y de México, por lo que de
Canada, USA and Mexico, a one-day marathon on
hecho fue un maratónico taller tetranacional en
n a n o t e c h n o l o g y. D o w n l o a d m a t e r i a l s f r o m
nanotecnología. Los materiales pueden descargarse de
http://www.cenam.mx/nwsn/
http://www.cenam.mx/nwsn/ .
SIM - PTB Workshop NMI - Metrology User Relation
Taller SIM - PTB Relación de los Institutos Nacionales
As a joint project by PTB, INMETRO, CENAM, OAS and
de Metrología con sus usuarios.
SIM, the workshop was held on March 2-5, 2009, in
Proyecto conjunto de PTB, INMETRO, CENAM, OEA y el
Querétaro, México, aimed to share tools for NMIs to
SIM, el taller se llevó a cabo del 2 al 5 de marzo de 2009, en
approach industries, taking some of the CENAM
Querétaro, México, con el objetivo de compartir algunas
experiences as a basis.
herramientas de acercamiento de los INM con la industria,
a partir de las experiencias del CENAM.
Reunión del QSWG
QSWG meeting
Con la hospitalidad del CENAMEP en Panama, Panama, el
Hosted by CENAMEP in Panama, Panama, on March 29,
29 de marzo de 2009 el QSWG elaboró su plan de
where a plan of activities was elaborated aimed at
actividades orientado a las actuales, y cambiantes
supporting the present, and changing, needs of the SIM
necesidades de los institutos nacionales de metrología del
NMIs to strengthen the quality management systems
SIM en materia de sistemas de gestión de calidad.
supporting assessed CMCs.
Reunión del QSTF
QSTF meeting
Celebrada en Panamá, Panamá, el 30 de marzo de 2009, y
Held in Panama, Panama, on March 30, 2009, reviews of
en la cual se revisaron sistemas de gestión de calidad
quality management systems (QMS) for new CMCs were
(SGC) para nuevas capacidades de medición y calibración
done and it was started the 5-year general reviews of the
(CMC) e iniciaron las revisiones quinquenales de los SGC
QMS as required by the CIPM-MRA.
requeridas por el CIPM-MRA.
Reunión del Consejo del SIM
SIM Council meeting
Celebrado el 2 de abril de 2009 en las instalaciones de la
Held on April 2, 2009 in the OAS premises in Washington,
OEA en Washington, D.C., el Consejo del SIM tomó la
D.C., among others, the SIM Council decided to use
decisión, entre otras, de llevar a cabo la Asamblea General
October 25-30 for the SIM General Assembly and related
del SIM y otras actividades del mismo del 25 al 30 de
SIM events in Peru.
octubre de 2009 en Perú.
VIII SEMETRO
VIII SEMETRO
The 8th. International Seminar on Electrical Metrology held
El 8th. International Seminar on Electrical Metrology tuvo
on June 17-19, 2009 in the city of Joao Pessoa, Brazil,
lugar del 17 al 19 de Junio, 2009 en la ciudad de Joao
organized by INMETRO and other institutions, where
Pessoa, Brasil, bajo los auspicios del INMETRO y otras
approximately 120 papers were presented by authors of 21
i n s t i t u c i o n e s , y e n e l c u a l s e p r e s e n t a r o n
countries.
aproximadamente 120 trabajos por autores de 21 países.
Prior to the VIII SEMETRO, four courses were delivered:
Previo al VIII SEMETRO se realizaron cuatro cursos:
47
·
"DC resistance Measurements", impartido el NIST.
·
"DC resistance Measurements" by NIST.
·
"AC-DC Thermal Transfer Standards and Calibrations"
·
"AC-DC Thermal Transfer Standards and Calibrations"
impartido por el NRC.
by NRC.
·
"Mediciones de Potencia y Energía" impartido por el
·
"Mediciones de Potencia y Energía" by UTE.
·
"Mediciones de tensión eléctrica de alta exactitud" by
UTE. “
CENAM.
·
"Mediciones de tensión eléctrica de alta exactitud"
impartido por el CENAM.
Electricity and Magnetism Working Group Meeting,
Reunión del grupo de trabajo de electricidad y
Among others, it was reported that the conclusions of the
magnetismo del SIM
comparison SIM.EM-S2 on electrical energy piloted by
Se informó del término de la comparación SIM.EM-S2 en
NIST was reported in INFOSIM. The AC/DC piloted by
energía eléctrica para la cual el NIST fungió como piloto y
CENAM was also completed and reported in the BIPM
cuyos resultados se publicaron en el número anterior del
INFOSIM. Los resultados de la comparación sobre AC/DC
KCDB. Other comparisons going on include capacitance,
están ya publicados en la KCDB del BIPM. Otras
multimeters, resistance and inductance. A number of
comparaciones en proceso incluyen capacitancia,
proposals for other comparisons are being considered.
multímetros, resistencia e inductancia. Un número
importante de propuestas de comparación están siendo
Mass comparison in CAMET
actualmente consideradas.
The starting meeting for the pilot study on mass
measurements aimed to the members of CAMET took
Comparación de masa en CAMET
place on November 17-21, 2008 in LACOMET, Costa Rica.
Del 17 al 21 de noviembre de 2008, se realizó en
CENAM will measure the traveling standards and will
LACOMET, Costa Rica, la reunión de inicio del estudio
provide the reference value for the study.
piloto para mediciones de masa de laboratorios nacionales
de la región de CAMET. El CENAM participa
caracterizando los patrones viajeros y aportando el valor
ONCOMING …
de referencia para dicho ejercicio.
Third Tri-National Conference of the North American
PRÓXIMAMENTE …
Coordinate Metrology Association and Sexta Reunión
- Taller de la Asociación Mexicana de Metrología de
Third Tri-National Conference of the North American
Coordenadas.
Coordinate Metrology Association and Sexta Reunión -
This Conference is jointly promoted by Canada, Mexico
Taller de la Asociación Mexicana de Metrología de
and the United States to be held on September 17-18,
Coordenadas
2009, in Queretaro, Mexico. Speakers will attend from
Promovida por Canadá, Estados Unidos de América y
Brazil, Canada, France, Germany, USA and Mexico. An
México, se celebrará en Querétaro, México, los días 17 y
equipment exhibit will also be part of the event.
18 de septiembre, 2009, con conferencistas de Brasil,
Further information on www.cenam.mx.
Canadá, Estados Unidos de América, Francia, Alemania y
México; así como exhibición de equipo.
QSTF meeting
Información adicional en www.cenam.mx.
To be held in Lima, Peru on October 27 and 28, 2009.
Reunión del QSTF
SIM Metrology School
A celebrarse en Lima, Perú, los días 27 y 28 de octubre de
To be tentatively held in the area of Rio de Janeiro, Brazil,
2009.
on December 9-16, 2009. Further information coming soon
on http://www.sim-metrologia.org.br/.
SIM Metrology School
A celebrarse en la región de Rio de Janeiro, Brasil,
4th. Tri-national Workshop on Standards for
tentativamente del 9 al 16 de diciembre de 2009.
Nanotechnologies,
Más información aparecerá pronto en http://www.sim-
To be held on February 3 and 4, 2010 in Ottawa, Canada.
metrologia.org.br/
Further information Jennifer.Decker@nrc-cnrc.gc.ca
This event will also provide an opportunity for the ISO TC
4th. Tri-national Workshop on Standards for
229 Nanotechnologies working group on the standard
Nanotechnologies,
about artificial gratings to meet.
Por realizarse los días 3 y 4 de febrero de 2010 en Ottawa,
Canadá.
Mayores informes Jennifer.Decker@nrc-cnrc.gc.ca
Adicionalmente, se reunirá el grupo de trabajo que elabora
la norma sobre rejillas artificiales del ISO TC 229
Nanotechnologies.
48
Nota Informativa
SOBRE LA POSIBLE REDEFINICIÓN DEL KILOGRAMO
Luis Omar Becerra Santiago
Centro Nacional de Metrología
Km 4,5 Carretera a los Cués, 76246, Querétaro, México
lbecerra@cenam.mx
El kilogramo, unidad de masa del Sistema
Debido a ello se han propuesto alternativas en
Internacional de Unidades (SI), es la única unidad
donde la definición de la unidad de masa esté
cuya definición se mantiene sin cambio desde su
basada en alguna constante física que pueda
adopción en 1901.
reproducir el valor de esta magnitud con una
incertidumbre aceptable para las necesidades de
Un kilogramo esta definido como la masa igual a la
los usuarios finales, (p.e. en control de procesos o
del prototipo internacional del kilogramo, que es
compra venta de productos, etc.).
un cilindro de metal (Pt-Ir). Este cilindro de 39 mm
de altura por 39 mm de diámetro, por ser un
Existe la posibilidad de que la nueva definición del
objeto, esta expuesto a daño físico y a la
kilogramo se adopte en la 24ª reunión de la
contaminación, lo cual es una amenaza para la
Conferencia General de Pesas y Medidas en el
conservación de la masa que define y por lo tanto,
2011 [2], y para ello son dos experimentos que
a la referencia de esta unidad de base del SI [1].
llevan la delantera en la tarea de redefinir el
kilogramo, el primero de ellos es conocido como el
experimento de la balanza de Watt y el otro es
conocido como el proyecto de la constante de
Avogadro [1].
El experimento de la balanza de Watt consiste en
la comparación de la potencia mecánica con la
potencia eléctrica, este proyecto se encuentra
1
activo actualmente en el NPL-Reino Unido , en el
NIST-Estado Unidos, METAS-Suiza, LNE-Francia
y en el BIPM-Oficina Internacional.
Fig. 1. Prototipo Internacional del kilogramo conservado en
la Oficina Internacional de Pesas y Medidas ubicada en
Sèvres Francia.
Fig. 2. Balanza de Watt del NIST- Estados Unidos.
1 La balanza de Watt del NPL-Reino Unido será transferida al NRC-Canadá en el transcurso del 2009.
49
El proyecto de la constante de Avogadro consiste
probablemente será determinado por la
en definir el kilogramo como un número definido
realización de alguno de estos dos experimentos:
de átomos de algún material, p.e. carbono 12.
La balanza de Watt o el proyecto de la constante
Este es un proyecto multinacional que trabaja bajo
de Avogadro.
la supervisión del Grupo de Trabajo de la
Constante de Avogadro (WGAC) del Comité
Consultivo de Masa (CCM).
La determinación experimental de la constante de
Avogadro vía el silicio, esta basado en mediciones
a esferas de monocristal de silicio de
aproximadamente 1 kg.
Fig. 4. Patrón Nacional de Masa de México, prototipo de
platino iridio k21 conservado en el CENAM.
Referencias
Fig. 3. Esfera de monocristal de silicio.
[1] Mill I. M. et al. Redefinition of the kilogram: a
decision whose time has come, Metrologia 42
(2005) 71-80
Actualmente existe una discrepancia del orden de
[2] Consultative Committee for Mass and Related
una parte en un millón (1x10-6) [2] entre los
Quantities (CCM), Report of the 9th meeting
resultados obtenidos en ambos experimentos, y
(28-29 April 2005) to the International
debido a ello el CCM recomendó que previo a la
Committee for Weights and Measures,
redefinición de la unidad de masa, esta
www.bipm.fr/utils/common/pdf/CCM9.pdf
discrepancia debe ser resuelta y que la
incertidumbre de la realización del kilogramo sea
igual o menor a 2 x 10-8 [2].
Ligas de interés
Una más de las recomendaciones del CCM, es
http://www.nist.gov/public_affairs/releases/electrokilog
que la nueva definición del kilogramo debe
ram.htm
mantener la referencia de la definición actual, lo
http://www.bipm.org/en/scientific/elec/watt_balance/
cual implica que al nivel de los usuarios finales,
Ud. o yo, cuando compremos un kilogramo de
http://www.npl.co.uk/engineering-
cualquier producto, siga siendo en esencia la
measurements/mass-force-
misma cantidad de masa que hemos estado
pressure/mass/research/npl-watt-balance
recibiendo. En cada país, los resultados de estas
mediciones de masa seguirán siendo trazables al
http://www.acpo.csiro.au/avogadro.htm
v a l o r d e l p a t r ó n n a c i o n a l d e m a s a
correspondiente, sólo que el valor de éste muy
50
INFOSIM ES UN MEDIO DE
INFOSIM IS A PUBLICATION
COMUNICACIÓN Y DIVULGACIÓN AL
COORDINATED BY THE
SERVICIO DEL SISTEMA
INTERAMERICAN METROLOGY
INTERAMERICANO DE METROLOGÍA
SYSTEM AND SPONSORED BY THE
(SIM) PATROCINADO POR LA
ORGANIZATION OF AMERICAN STATES
ORGANIZACIÓN DE ESTADOS
(OAS).
AMERICANOS (OEA).
PARTIAL OR TOTAL REPRODUCTION OF
SE AUTORIZA LA REPRODUCCIÓN
ITS CONTENTS IS AUTHORIZED AS
PARCIAL O TOTAL DEL CONTENIDO
LONG AS CREDIT IS GIVEN TO THE
MENCIONANDO LA FUENTE.
SOURCE.
Agosto 2009
August 2009
www.sim-metrologia.org.br/
INFO IM
INFORMES
INFORMATION
km 4,5 carretera a Los Cués, El Marqués Qro., C.P. 76241, Querétaro, México
Tels. +52 (442) 211 05 00 al 04 Fax: +52 (442) 215 39 04
Document Outline
