| 摘要 |
PURPOSE:To make a titled device difficult to receive the influence of DC level change and DC drift by differentiating the signals of prescribed waveforms of a constant frequency and a constant amplitude in a differentiating circuit including an unknown capacitance in digital multimeters or the like, and utilizing the peak value of the amplitude of the differentiated signals. CONSTITUTION:A signal source 10 generates a signal e1 having a prescribed waveform such as a triangular wave of a constant frequency and a constant amplitude at a low impedance. This signal e1 is differntiated by a CR differentiating circuit 14 including an unknown impedance element C and the resultant signal e3 is applied to a peak voltmeter 12. The peak value of the amplitude of the differentiated signal obtained from the above-mentioned circuit 14 can be taken relatively large as compared to the amplitude of the inputted triangle wave signal, and the peak value of this differentiated signal is proportional to the unknown capacitance value over a wide amplitude range. Thereby, the amplification factor (sensitivity) of the voltmeter circuit measuring the unknown capacitance can be made relatively low, and therefore the influence of the DC drift or the like of the voltmeter is reduced. |
