A Radio-Frequency Bridge for Impedance Measurements from 400 Kilocycles to 60 Megacycles

A radio-frequency bridge for measuring low impedances is described. Through modification of the conventional Schering bridge a new circuit has been developed that measures both resistive and reactive components in terms of incremental values of capacitance. A direct-reading range of 0 to 1000 ohms resistance and 0 to 4000 ohms reactance is provided at a frequency of 1 megacycle. The resistance range is independent of frequency and the reactance range varies inversely with frequency. The sources of error are discussed and typical measurements at frequencies up to 60 megacycles given.