Rf Inductance Meter

16 RF INDUCTANCE METER J. Bareford It is a downright shame not to be able to use many of your inductors simply because their value is not known. First in a new series of budget test equipment for the home constructor, the RF inductance meter leaves coloured bands and unfamiliar codes on high-frequency inductors for what they are, and gives a reliable indication of inductance as well as relative Q (quality) factor on an analogue scale. The usable range extends from about 50 nH to 4 mH. The present inductance meter is intended for high-frequency inductors, and for this reason it is based on a measuring method rather different from that of the digital inductance meter described in Ref. 1. The principle adopted here is applying a known frequency to an L-C tuned circuit of which the inductance, L, is unknown, and the capacitance, C, is variable but cali- brated. At a certain value of C, the tuned circuit resonates, which is detected by means of a signal rectifier. The value of C requir...