Frequency measuring circuit for multi-phase current network

摘要

The circuit has a threshold stage (SW) supplied with a difference signal obtained from 2 phases of the multi-phase network input voltage, for providing a frequency-proportional sequence of rectangular pulses with a hysteresis dependent on the amplitude of the input voltage. The threshold stage uses operational amplifiers (V4,V5) supplied with reference voltages via a symmetrical charge circuit (R2,V2,C1 ; R4,V3,C2), the rectangular pulses provided by a flip-flop circuit (V6,V7).