A ratio transformer bridge for the measurement of low-loss tangents

The authors discuss the architecture of transformer ratio bridges for measuring the loss angles of low-loss dielectrics and describe the development of a sensitive and accurate bridge, capable of measuring loss angles with a sensitivity of 1*10/sup -8/ (S/N=1 at a detector bandwidth of 1 Hz) and an accuracy of a few parts in 10/sup -7/. The bridge is computer controlled and has an automatic capacitive balance. Its main characteristics and their influence on sensitivity and accuracy are discussed. As an example, measurements as functions of temperature and frequency are presented.<>