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.

I. Introduction

Following the successful implementation of Programmable Josephson Voltage Standards at 10 V [1], [2], it is foreseeable that systems based on stable quantum voltage steps will in the future progressively replace the conventional Josephson voltage standard (CJVS) systems based on metastable, zero-crossing quantum voltage steps. PJVS systems have the potential to bring to the field of voltage metrology accuracy equivalent to CJVS, improved ease of use, and new measurement capabilities that exploit the intrinsic stability and programmability of their voltages. However, a number of precautions need to be followed in order to limit the magnitude of errors at the output of the probe [3].