3. Resistance standards

3.1 Resistance standard based on the quantum Hall effect

The quantum Hall effect (QHE), discovered by Klaus von Klitzing in 1980 [25] , is observed on a two-dimensional electron gas (GE2D) placed at very low temperature (T < 4.2 K) and under high magnetic flux density (B > 1 T). The GE2D has a Hall resistance, the ratio of Hall voltage to current, which can take on quantized values depending only on the fundamental constant h/e ² :

where i is an integer. For...