Four amplifiers are used in this circuit, which uses a magnetic pickup to obtain the pulses whose ratio is to be determined. The circuit is supplied with a voltage of 12 V, with three functions being observed in the circuit. At the entrance we have an amplifier with hysteresis to conform the signals captured by the magnetic transducer. Two amplifiers are connected as a monostable multivibrator with time constant given by: 0.7 x R1 x C1, to obtain pulses of constant duration in the next step. This step consists of a circuit that obtains an output voltage proportional to the average of the input pulses, according to the formulas given in the circuit itself, which has an adjustable element that allows it to be adapted to the frequency of the signals captured. The circuit can be used as an input shield.
