A High-Resolution PXI Digitizer for a Low-Value-Resistor Calibration System

This paper characterizes the metrological properties of a dual-channel high-resolution digitizer designed for use in a system to calibrate standard resistors with values between 1 m Ω and 10 Ω at frequencies from 40 Hz to 10 kHz. The possibility of using a digitizer to measure the complex voltage ratio is analyzed for both digitizer operating modes: the dual-channel mode with a simultaneous sampling and the single-channel mode with a sequential sampling in which an additional external multiplexer is used. The method of acquiring samples presented in this paper was used to investigate and compare the short-time stability and temperature influences on the metrological properties of the digitizer. This makes it possible to reduce the influence of the instability of the generator, being the signal source for the tested digitizer, on the research results. Moreover, presented in this paper are the frequency characteristics of the magnitude and phase of the complex voltage ratio, as well as the research results of the digitizer linearity and the phase measurement accuracy. All measurements discussed here were performed for both digitizer operating modes.