Condenser Frequency Counter
Today you can find capacitor frequency meters in the ranges included in the interval from 10 Hz to 10 MHz. The principle of operation of these devices is based on the alternation of the processes of charge and discharge of the capacitor. The capacitor is charged by the battery, then discharged to the electromechanical system.
The frequency of charge-discharge repetitions coincides with the frequency of the signal under study, because the measured signal itself sets the impulse to switch. We know that the charge CU flows in one working cycle, therefore the current flowing through the magnetoelectric system is proportional to the frequency. Thus, amps are proportional to hertz.