Electrical Quantum Standards

The laboratory realizes the electrical units and conducts the necessary research and development program.

With the definition of the ampere in the SI, the magnitude of all the other electrical units is determined. The practical realisation is made by the application of the known laws of physics. The theory of electromagnetism permits the construction of, for example, volt, current and watt balances, and calculable capacitors, which can furnish accurate absolute values for voltage, current, capacitance and resistance. The experiments involved are very expensive and are, therefore, only conducted by a limited number of national metrology institutes.

Electrical Quantum Effect

With the discovery of the Josephson effect and later the quantum Hall effect, the possibility opened up in metrology of producing high-precision reference values for electrical voltage and electrical resistance without the need for difficult mechanical experiments. The reproducibility of these reference values became soon much better than their absolute realisation within the SI. This situation has led to the fact that the Comité International des Poids et Mesures (CIPM), at the behest of the Comité Consultatif d'Électricité (CCE), determined a standard value for the Josephson constant K _J and the von-Klitzing constant R _K. The absolute measurement uncertainty of these constants, due to the above-mentioned difficulties encountered in absolute experiments, is about a hundred times worse than the reproducibility that the quantum experiments permit. The use of the Josephson effect and the quantum Hall effect has resulted in a worldwide improvement and standardisation of electrical calibration results.

The METAS operates a Josephson voltage standard, and a resistance standard based on the quantum Hall effect. Both experiments are under constant further development and kept up to date with the latest developments in the field.

The laboratory works in the following research and development projects:

Application of the quantum Hall effect as a primary standard of ac resistance
Realization of a primary standard of ac voltage based on the Josephson effect
Realization of a primary standard of capacitance based on the single tunneling effect