The principle of determining the capacitance of capacitors is in both cases made possiable with the comparative method, and both methods use the charge of the capacitor phenomenom . DC voltage capacitor charge time depends directly on capacitor capacitance. Thus, it is a clear interdependence of the capacitors capacity with the charging time of that capicator. -In the first circuit (power amplifier circuit in the deriving joint) capacitor charging area is "analyzed" by a derivative. At the output of the derivative, a value will be existant whole time until the input from the derivative is a constant value. The derivative itself is relatively unstable, and adding additional resistors and capacitors can improve its stability. Since the values at the output of the derivative are very small, the signal is amplified 100 times by the operating amplifier, and this value is the result of the measurement of the circuit. -The second circuit (circuit with PWM principle) uses a comparator circuit to get the solution. The circuit is based on pulse width modulation (PWM). The time constant of charging the capacitor turns into a rectangular pulse of the same amplitude but different widths. The voltage impulse or the mean value of the impulse voltage is directly dependent on the capacitance of the capacitor. The determination of the measuring range of capacitance can be displayed on a certain voltage dependent level. By using any TRMS equipment, a constant duty value is obtained from the duty cycle of the signal as an effective signal value. In order for the circuit to be applicable to any equipment, inductance is provided, which function is to approximately generate constant value from the non-constant signal. Furthermore, there is an amplifier, resistors and diodes, whose function is to obtain a capacitive-amplitude linear dependence on the final output from the circuit, which reaches values between 0-10V (since the voltage input in the programmable logic controllers is between 0-10V). -There are also many integrated circuits in the market that are using capacitive-voltage conversion.