Effect of Input Bandwidth of a Sampler on Differential Sampling Based on a Programmable Josephson Voltage Standard

We have investigated the response characteristics of two different samplers, Keysight 3458A and NI 5922 implemented in setup for differential sampling based on a programmable Josephson voltage standard, to input signals in a frequency range below 1 kHz. The RMS amplitudes measured with the samplers coincides within a few parts in 10
⁶
at frequencies below 100 Hz. However, the difference between the RMS values increases with the frequency, mainly due to the dramatic change of the value obtained with the Keysight 3458A. The difference reaches up to 25 μV/V at 1 kHz. The feature is inferred to originate from the difference in the input bandwidths for the two samplers.