A high precision and stable current source is used to drive a current through the inductive coil. The current is determined by measuring the voltage drop across a 100 Ω standard resistor connected in series with the coil. The standard resistor is periodically calibrated using a quantum Hall resistance standard. Two voltage reference systems based on 1.2 V and 2.5 V programmable Josephson arrays provided by NIST are available. They allow us to determine the voltage drop across the standard resistor and the induced voltage in the coil in direct opposition. They additionally allow the calibration of the precision commercial digital voltmeters which are employed as null detectors.
For further details see:
- Solve S., Chayramy R., and Stock M., A Bias Source for the Voltage Reference of the BIPM Watt Balance, IEEE Trans. Instrum. Meas., 2013, 62, 1594-1599.
- Bielsa F., Rolland B., Solve S., Li S., Kiss A., and Fang H., A programmable bias source for the PJVS in the BIPM Kibble Balance, Proc. CPEM 2018, 2018 (to be published).
|The 2.5 V programmable Josephson voltage standard|