A transformer-ratio bridge for the measurement of small loss angles

A development in the architecture of transformer-ratio bridges for the measurement of the loss angles of low-pass dielectrics is described. This has led to a sensitive and accurate bridge capable of measuring loss angles with a detection limit of 1×10^-8 rad (S /N=1 at a bandwidth of 1 Hz of the detector) and an accuracy of a few percent in the 10^-6 and higher ranges in the frequency range from 200 Hz to 200 kHz. The readout of the bridge is computer controlled and has an automatic capacitive balance. The most important characteristics of the bridge and their influence on the sensitivity and accuracy are discussed. Measurements as a function of frequency are presented as an example. The bridge can be used in numerous applications concerning the characterization of dielectric materials