GB2014320A - Measuring Reactance - Google Patents

Abstract

Current from a second circuit is balanced by current from a third circuit energised by a voltage dependent upon the current flowing in a first circuit, whereby the value of one reactance in either the first or third circuit can be determined from the values of components in the other circuits using the balance equation. In a first embodiment, the first circuit comprises a resistor R3, Fig. 5, and a capacitor Cx to be measured, the second comprises a resistor R2, both circuits being energised by a supply S1, and the current in the second circuit is opposed, in a tapped choke, by the current from a third circuit, comprising a standard capacitor C8, energised by a voltage, from an amplifier A, dependent upon the current in the first circuit. In a second embodiment (Fig. 6, not shown), the unknown and standard capacitors are effectively interchanged. Inductance can be measured similarly (Figs. 4 and 7, not shown), and when the unknown reactance is in the third circuit the zeroising resistor Gc, Fig. 5, can effectively be replaced by an additional amplifier and a coupling transformer (Figs. 7 and 8, not shown). <IMAGE>