The leakage resistance to ground of a NIST Programmable Josephson Voltage Standard

The Programmable Josephson Voltage Standard (PJVS) leakage resistance to ground (LRG) is defined as the electrical resistance of one side of the measurement leads to ground. Under certain measurement conditions, this resistance can produce a significant systematic voltage error of the measured value of the PJVS output voltage. In particular, if the low side of the array is grounded, for instance in a direct comparison measurement with another JVS, then the LRG will reduce the PJVS output voltage. At 10 V, an error of 0.5 nV can result from a LRG of 50 GΩ if the measurement leads have a total resistance of 2.5 Ω. The LRG and the path of the leakage current to ground are difficult to determine. Furthermore, its corresponding voltage error is still present while the bias source is in operation to control the PJVS. It is therefore important to apply different measurement techniques to compare the corresponding LRG values.