The Impact of the New SI on Industry

Jeff Gust

Chief Corporate Metrologist

Fluke Corporation

Learning Objectives

• Information on the SI redefinition• Approximate timeframe for redefinition• Will redefinition will potentially affect your

organization• The role of industry in educational activities

associated with the redefinition• How measurements associated with the

redefinition will be disseminated to industry

Introduction

• In October of 2011, the CGPM may meet to consider a proposal to address the definition of the kilogram

• Last of the seven base units defined in terms of a material artifact• Unchanged since 1889• ampere, mole and candela all defined in terms of the kilogram

Draft proposal of SI revision

• The ground state hyperfine splitting frequency of the caesium 133 atom Δυ(133Cs)hfs is exactly 9 192 631 770 hertz

• The speed of light in vacuum c is exactly 299 792 458 metre per second

• The Planck constant h is exactly 6.626 06X ×10-34 joule second• The elementary charge e is exactly 1.602 17X ×10-19 coulomb• The Boltzmann constant k is exactly 1.380 6X ×10-23 joule per kelvin

• The Avogadro constant NA is exactly 6.022 14X ×1023 reciprocal mole

• The luminous efficacy Kcd of monochromatic radiation of frequency 540 ×1012 Hz is exactly 683 Lumen per watt

• The values for x are to be added on the most recent CODATA adjustments

Draft proposal of SI revision

• The SI will continue to have the seven base units• The kilogram would be defined in terms of the Planck

constant• The ampere will be defined by the elementary charge• The kelvin will be defined by the Boltzmann constant• The mole will be defined in terms of the Avogadro

constant

Questions from industry

• When will this happen?• How much will it affect the reference values of

my standards, their associated uncertainty, and any measurement processes?

• Who is going to help explain what these changes are, and why they are occurring, to my company and to my customers?

• How will the change in the SI get disseminated to my organization?

When is this going to happen?

• Probably not very soon• The conditions of the 23rd meeting of the CGPM

in 2007 would have to be met– Independent experiments for Planck’s constant need

sufficient level of agreement in the watt balance results

– One excellent experimental result for the Boltzmann constant has been performed, a second independent experiment needs to confirm

• CGPM meets once every four years, 2011, 2015

How much will it affect the reference values of my standards?

• In order to realize the proposed definitions it will be necessary to develop mises en pratique

• Example: Ampere is realized through Ohm’s law through the Josephson and Quantum Hall effects

• Because of the redefinition of h and e, and the Josephson constant is based on the ratio 2e/h, the Josephson constant will also change– The effect is approximately 19 x 10-9

– Only seen by labs using JVS in Interlaboratory Comparisons

• Same for Von Klitzing constant, based on h/e2 – The effect is approximately 22 x 10-9 – Only seen by organizations that send their best resistors to NMI’s

• The effect for Mass not known yet, anticipated to be a few parts in 108 – Only seen at best NMI to industry interactions

How much will it affect the reference values of my standards?

• The mole moves from the kilogram to Avogadro constant– Not anticipated to change by more than few parts in 109

• The Candela is defined in W/sr, tied to kilogram, same shift as for kilogram applies

• Kelvin moves from Triple Point of Water (TPW) to Boltzmann constant– Once definition changes, TPW becomes a quantity to be determined

experimentally– Boltzmann constant has 1 x 10-6 uncertainty, which is approximately

0.25 mK– Most industry and NMI uncertainty for TPW is less than 0.1 mK– No present solution, but possibly can be added as a covariant term that

drops out

• It would be beneficial if the CIPM and NMI’s partner with industry to develop educational materials at appropriate levels of complexity

• Two potential candidates from industry would be NCSLI and Fluke

• Fluke played a critical role in the latest Boltzmann project to determine the constant by dielectric constant gas thermometry

Who is going to help explain what these changes are?

• Fluke has a history of addressing these type of issues

• 1990 volt shifted 9.264 x 10-6 and ohm shifted 1.69 x 10-6

• Volt shift was approximately 100% of the 1 year specification of the Fluke 5700A

• Fluke Application note was developed to communicate the change

Who is going to help explain what these changes are?

• One possible method of outreach is through social media

Who is going to help explain what these changes are?

Who is going to help explain what these changes are?

• NCSLI could be a major contributor in education and outreach on the subject

• In 1989, NCSL formed Technical Advisory Group 91.4.1 to address the 1990 Volt and ohm changes

• Membership from various sections of NCSL• The committee developed a document on practical guidance for

implementation of the changes, and sent speakers out around the U.S. NCSL meetings to provide a forum for Q and A

How will the change in the SI get disseminated to my organization?

• Needs to be a planned activity• Educational activities should help organizations identify if they are

affected• Dissemination activities could be classified as:

– Organizations that perform calibration services whose reference value and uncertainty are affected by redefinition (Traceability Provider)

– Organizations that own and utilize devices whose reference values and uncertainty would be affected by redefinition (Traceability User)

• Users need to coordinate with Providers• Providers may be able to start providing redefined calibrations

before the effective date• Reports would clearly need to indicate which definition was used

How will the change in the SI get disseminated to my organization?

• Example – the SI 1990 logo was developed by NCSL for use on equipment and reports performed under the new definition

Conclusion

• Redefinition is probably not imminent• As we progress towards redefinition, it will be important to consider

the repercussions of new definitions and mises en pratique• Plans must be developed and executed in order to educate and

disseminate knowledge