Precision measurement of phasors in electric networks as a function of frequency

Measurement of phasor relationships in networks is considered in general, and a system is described which accomplishes this task. Numerical examples for purposes of orientation are given. Detection is based on the performance of a phase-sensitive rectifier of the ring modulator type. A system is described, using a pair of such detectors being polarized by two auxiliary voltages, of the frequency under consideration, the voltages being in time quadrature to each other. In this manner true null detection is accomplished unambiguously. The differential polarized rectifier, the polarizing supply circuit, and the required auxiliary amplifiers, containing means of amplitude-and-phase adjustment, are discussed briefly. Operation in the frequency range of 1 to 1,000 cycles for input signals of the order of 100 microvolts and for extremely adverse signal-to-noise ratios is accomplished with an over-all accuracy of 1 per cent.