Frequency transducer

Abstract

A frequency transducer for monitoring frequency in a power line wherein a frequency representative signal is generated which is twice the frequency of the signal to be monitored in the power line, the frequency representative signal is shaped into a triggering output signal which is supplied as one input to a comparator in a comparator/timer circuit. A second input to the comparator is provided by a timing circuit which produces a reference signal as that second input, said reference signal having a constant non-zero duration, the magnitude of which is dependent upon the timing constant of a resistive-capacitive circuit; said resistive-capacitive circuit being charged by a constant charging current of high value to ensure that variances in the timing constant due to temperature, humidity, contamination and the like are small when considered as a percentage figure. Switching means within the comparator/timer circuit are responsive to the output of the comparator in that circuit to drive the comparator/timer circuit and to produce a stabilized frequency representative signal which is then averaged and amplified to produced an averaged frequency representative DC signal directly proportional to the frequency of the signal carried by the power line.