Digital impedance bridge based on a two-phase generator

A digital impedance bridge composed of two digital sine-wave generators and inductive voltage dividers (IVD's) designed for precision comparison of different impedance standards is described. To increase the reliability of measurement and its accuracy, an unknown is compared to many reference standards and a special method of estimation is applied. The bridge enables one to measure impedance from 10 /spl Omega/ up to 100 k/spl Omega/ in the frequency range between 100 Hz and 1 kHz with a relative uncertainty smaller than 50 /spl mu//spl Omega///spl Omega/ which is mainly due to short term instability of the digital source and uncertainty of reference standards.