A Reconfigurable Four Terminal-Pair Digitally Assisted and Fully Digital Impedance Ratio Bridge

A reconfigurable digital bridge for calibrating four terminal-pair (4-TP) defined impedance standards in the whole complex impedance plane by means of fully digital (FD) operation of the bridge and for R-R,C-C calibration and ac quantized Hall resistance experiments by involving reference inductive voltage divider in digitally assisted (DA) configuration has been built at CMI in recent years. For the purposes of the bridge, high-accuracy digital voltage sources operating in the audio frequency range with full isolation between modules and with battery operation mode have been developed. Together with coaxial switches with negligible crosstalk between channels, the voltage sources form the basis for full automation of the calibration process. The bridge has been tested in both FD and DA configurations. Depending on the configuration, different relative accuracies of the measurements can be achieved in the range from a few parts in 10
⁸
to a few parts in 10
⁵
.