Josephson Array Voltage and Quantum Hall Resistance Standard
Primary Standards for Realization of the ampere – programmable Josephson voltage standard (PJVS) and quantized Hall resistance standard (QHR)
Photo of the SCL programmable Josephson array voltage standard (PJVS)
Photo of the SCL quantized Hall resistance standard (QHR)
The SCL programmable Josephson array voltage standard (PJVS) is an instrument that generates SI derived unit of electric potential difference (voltage) based on Josephson effect. By fixing the numerical value of electric charge (e) and plank constant (h), the realized voltage can be calculated by the Josephson constant (KJ=2e/h). The Josephson effect can be realized in the laboratory environment by high purity liquid helium with operating temperature at about 4.2 K and with the presence of high frequency signal of about 20GHz.
The SCL quantized Hall resistance standard (QHR) is an instrument that generates SI derived unit of electric resistance based on quantum Hall effect. Similar to the Josephson constant, the realized electric resistance can be calculated by the von Klitzing constant (RK = h/e2). The quantum Hall effect can be realized in the laboratory environment by high purity liquid helium and pumping mechanism to achieve temperature of about 1.2 K and with the presence of high magnetic field up to 10 T.
At SCL, the SI base unit of electric current is realised using Ohm's law with practical realizations of the SI derived unites of voltage and resistance based on the Josephson and quantum Hall effects. The PJVS and QHR are used to calibrate laboratory's reference voltage standards and standard resistors respectively, which established the traceability of DC electric quantities to the SI units.
Traceability chart for the realization of the electric current
Reference
- Mise en pratique for the definition of the ampere and other electric units in the SI, prepared by the CCEM.