An AC-DC Ratiometer and Its Use in a CRL Meter

An impedance meter is described which measures dc resistance and ac capacitance and inductance. It uses an ac-dc ratiometer capable of high accuracy and good noise immunity. The ratiometer is a combination of a dual-slope integrator and an integrating phase-sensitive detector. The ratio, which is displayed on a counter, is the number of denominator signal samples required to offset a prescribed number of numerator samples. The remainder output, if important, can be evaluated by a sinple dual-slope integrator to provide the readout digits of lesser significance. The same circuit is used for both ac and dc ratios and could be used to detennine the ratio of the average value of an ac voltage to a dc voltge.