GB735915A - Improvements in or relating to alternating current bridges - Google Patents

Abstract

735,915. Measuring bridges; transfer impedance and admittance measurements. WAYNE KERR LABORATORIES, Ltd., and CALVERT, R. April 2, 1954 [April 10, 1953], No. 9762/53. Class 37. In an A.C. bridge circuit for measuring the transfer admittance of a network given by I=YE where Y is the required admittance, E the input voltage and I the output current at fixed or variable frequencies, an A.C. energized input transformer 10 has a variably tapped secondary 12 energizing the unknown network 15 whose output current energizes the variably tapped primary 17 of output transformer 18; and also a variably tapped secondary 23 which is connected directly to an intermediately variable tap 21 of a second primary 22 of transformer 18, and also connected to a standard variable resistance 24 and a standard variable capacitance 25 the free ends of which are selectively connectible over switches 26, 27 to either end of the primary 22. The secondary of transformer 18 is connected to an unbalance detector and the standard variables are adjusted separately until the output is zero, when the transfer admittance of the network is equivalent to the transfer admittance of the standard variables combined with regard to the phase quadrant in which each is connected by switches 26, 27, multiplied by a factor dependent on the tapping positions of windings 12, 17 and 13, 22. The standard variable capacitance is replaceable by a corresponding variable inductance switched in phase opposition thereto, and the system is applicable to the determination of transfer impedance by energizing winding 17 not from the output current of the unknown network but from the current flowing thereto from winding 12.