DC and AC quantum Hall measurements
- Bureau International des Poids et Mesures, Sevres (France)
The quantum Hall effect (QHE) is now widely used by national laboratories to establish a reference standard of dc resistance featuring low uncertainty with respect to the ohm and very high reproducibility. For high quality QHE samples, the reproducibility of the quantized Hall resistance (QHR), measured at dc or at very low frequencies (of order 1 Hz), is of order 1 part in 10{sup 9}. Accurate resistance-ratio measurement techniques have been developed to calibrate conventional resistance standards (in particular 1{Omega}, 100 {Omega} and 10 k{Omega} standards) in terms of the QHR, with uncertainties not higher than a few parts in 10{sup 9}. The following techniques are reviewed: dc cryogenic current comparators bridges, low frequency ac cryogenic current comparator bridges and low frequency ac bridges using high permeability magnetic cores and operating at room temperature. Sources of uncertainties and limitations in the resolution of the measurements are discussed. The technique of connecting QHE samples in series or in parallel using multiple links is also discussed. This technique provides highly accurate equivalent QHRs which are multiples or submultiples of the individual QHRs. In the case of parallel connections, the total measuring current which can be passed through the samples is increased, resulting in improved resolution of the measurements.
- OSTI ID:
- 125695
- Report Number(s):
- CONF-940603-; TRN: 95:005769-0062
- Resource Relation:
- Conference: CPEM `94: conference on precision electromagnetic measurements, Boulder, CO (United States), 27 Jun - 1 Jul 1994; Other Information: PBD: 1994; Related Information: Is Part Of 1994 Conference on precision electromagnetic measurements digest; DeWeese, E.; Bennett, G. [eds.]; PB: 577 p.
- Country of Publication:
- United States
- Language:
- English
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