Monitoring the U.S. legal unit of resistance via the quantum Hall effect
Open Access
- 1 June 1987
- journal article
- Published by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Transactions on Instrumentation and Measurement
- Vol. IM-36 (2) , 222-225
- https://doi.org/10.1109/TIM.1987.6312673
Abstract
The quantum Hall effect is being used to monitor the resistances of the five 1-Ω Thomas-type resistors which define the U.S. legal unit of resistance, the ohm maintained at the National Bureau of Standards (ΩNBS). Typically, the total one-standard-deviation (1σ) accuracy for the transfer between three different GaAs quantum Hall devices and the five 1-Ω resistors is ±0.05 ppm. Measurements to date provide the first direct evidence that the value of ΩNBS is decreasing by about (0.05 ± 0.02) ppm per year.Keywords
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