A Measurement of the NBS Electrical Watt in SI Units

Olsen,; Elmquist,; Phillips, M. R.; Williams, Stefan B.; Jones, Jones; Bower,

doi:10.1109/cpem.1988.671332

Cited by 11 publications

(15 citation statements)

References 2 publications

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“…Fortunately, we have two ways to measure this profile, from the quotient versus displacement or from the quotient versus displacement. In our previous work [3] the quotient profile was used exclusively, but the measurement is time consuming and subject to hysteretic effects in the knife edge. Alternatively, measuring the quotient over 0.1 mm intervals produces an 800 point profile with typically 100 W/W noise.…”

Section: B Force-current (F/i) Quotientmentioning

confidence: 99%

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The NIST watt balance: progress toward monitoring the kilogram

Steiner

Gillespie

Fujii

et al. 1997

IEEE Trans. Instrum. Meas.

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The National Institute of Standards and Technology (NIST) watt balance is an experiment to compare measurements of the watt using electrical references (volt, ohm) to those using mechanical references (length, time, mass). A coil within a radial magnetic field has a dual use of: 1) generating a voltage by moving at some velocity to calibrate the magnetic flux density, and, 2) generating a force with electrical current to balance the gravitational force of a mass. This experiment has had several improvements made to it in the last year. These include the incorporation of three-laser interferometry and a refractometer to improve the velocity measurements, temperature control and coil rotation damping to reduce drifts and stabilize laser and mechanical alignments, and a gravimeter to determine local gravity. Systematic errors and scatter in long-term measurements have been greatly reduced in the last year, but statistically significant deviations relative to within-run uncertainty still persist. The source of these deviations has not yet been identified. Recent within-run standard deviations are generally near 0.1 W/W, which is the target precision of this present design.

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Section: B Force-current (F/i) Quotientmentioning

confidence: 99%

“…The same quantity of power is calculated from the measured electrical and mechanical quantities, by comparing the force times the velocity to the voltage times the current. As an indication of its earlier accuracy, the 1988 NIST value for the watt derived from this basic design had a relative combined standard uncertainty of 1.3 W/W [3].…”

Section: Introductionmentioning

confidence: 98%

The NIST watt balance: progress toward monitoring the kilogram

Steiner

Gillespie

Fujii

et al. 1997

IEEE Trans. Instrum. Meas.

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“…The discontinuity in the value of the kilogram introduced by the new definition would thus be limited to this amount. Based on the results to date from the moving-coil force balance measurements of 2e/h at the National Physical Laboratory, U.K. [ 5 ] , and the National Bureau of Stan-U.S. Government work not protected by U.S. copyright dards, U.S. [6], such an uncertainty for 2 e / h does not seem totally out of reach. A new definition of the kilogram derived from precision electromagnetic measurements could be the subject of a talk at a CPEM in the first decade of the 21st century!'…”

Section: Electromagnetic Measurements and The Fundamental Constantmentioning

confidence: 99%

Basic standards and fundamental constants

Taylor

1989

IEEE Trans. Instrum. Meas.

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These introductory remarks to the panel discussion on Basic Standards and Fundamental Constants at the 1988 Conference on Precision Electromagnetic Measurements (CPEM) touch upon two topics: the importance of precision electromagnetic measnrements to the fundamental constants and vice versa; and the idea that recent advances in the determination of a number of constants may have made future least squares adjustments of the constants unnecessary.

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“…One of the devices used to relate the mechanical and electrical units is the watt-balance apparatus [ 11- [4]. This apparatus compares the force of a mass in gravity to the force on a current in a magnetic field.…”

Section: Introductionmentioning

confidence: 99%

“…Now that the longterm stability for maintaining the electrical units is greater than that for maintaining the mass unit lo-' for voltage and resistance versus ,lo-* for the kg), can the watt-balance be used, in reverse, to monitor the stability of the mass standard? That is the proposal of B. Kibble in [2] and the purpose of a project in the UK [l], [21 and one in the U.S. [31, [4].…”

Section: Introductionmentioning

confidence: 99%