Method for the Measurement of "Q"

The quality of ferrite materials has improved markedly over the last few years. Inductor "Q\´s" of 500 to 700 at frequencies of 100 to 200 kilocycles appear quite frequently in filter designs. Techniques of measurement of the storage factor Q, however, have not kept pace. The residual phase angle in bridges and the series and parallel damping in Q meters cause considerable error. For this reason these instruments are usually used as comparators rather than absolute measuring instruments. The references in this comparison are usually inductors which are known to work well when assembled as filters. The method described in this paper avoids, to a large extent, detrimental influences of the measuring circuit on the test. For this reason Q values of 500 to 1000 can be measured with reasonable accuracy. The method is intended to be a reference for relative measurements.