GB661338A - Improvements in impedance measuring - Google Patents

Abstract

661,338. Impedance and power factor measurements. RADIO CORPORATION OF AMERICA. July 26. 1949 [July 27,1948], No. 19636/49. Class 37. The resistive and reactive components of an unknown impedance, as well as the loss angle of paramagnetic core material, are measured by developing a voltage determined by the impedance, developing voltages corresponding to the resistive and reactive components of this voltage, and adjusting their magnitudes to balance the first voltage and produce a null indication. The impedance 32, Fig. 1, to be measured is connected in series with the primary winding 12 of a vario-coupler 10 and a resistor 16 across a source of alternating voltage 34. A second vario-coupler 18 has its primary winding 20, shunted by a capacitor 26, connected in series with a resistor 24 across the source 34. The secondary windings 14, 22 of the vario-couplers 10, 18 are connected across the terminals 28, 30 of the impedance 32 in series with an ammeter 36. The vario-coupler 10 is adjusted to give a minimum current through the instrument 36, its setting then giving the value of the reactive component of the impedance 32. The vario-coupler 18 is then adjusted to give a minimum current through the instrument 36, its setting then giving the value of the resistive component of the impedance 32. In a modification, Fig. 2, for determining the loss angle of a paramagnetic core 40, the impedance 32 is replaced by a primary winding 38 on the core 40, a secondary winding 42 being connected in series with the secondary windings 14, 22 and the instrument 36. The vario-couplers 10, 18 are adjusted to balance the reactive and resistive components of the voltage induced in the secondary winding 42, the ratio of the resistive to the reactive component giving the tangent of the loss angle of the core 40. The windings 38, 42 may each consist of a single turn. For use at high frequencies two sections of wave-guide 40, 42, Fig. 3, are provided for each of the variocouplers. The primary windings 12, 20 are fixed in the guides, the secondary windings 14, 22 being slidably mounted for balancing. Electrostatic couplings may be employed instead of electromagnetic.