Digital-analog frequency error signaling

Abstract From the Canadian patent

of Disclosure, A frequency or speed error circuit for producing a dc. voltage which in polarity and magnitude varies according to the sense and the size of the error between a variable input frequency and a set point frequency. The period of successive cycles of the variable frequency incoming signal is digitally compared with a fixed predetermined, time interval measured off by a precision standard interval generator to produce pulses which vary in width according to the magnitude of the error. The latter pulses are treated as negative or positive when the variable period is shorter or longer than the standard time interval and are algebraically summed by an operational amplifier having a …