Method of Measuring Voltage without Cable Correction by Loading Capacitance Changeable CVP

Capacitive voltage probe (CVP) can measure the common mode disturbance voltages without contact to cables. However, it is necessary to obtain the correction factor for each cable within correction. Although the measurement method using two CVPs has been developed to measure the voltage without the correction, it needs two CVPs and a signal generator. This paper proposes the measurement method without correction using the loading capacitance changeable CVP (LCC-CVP). To evaluate the performance, a cable was replaced with a copper rod, and the deviation from the actual common mode voltage was measured. The results indicated that the deviation was within 3dB from 0.15 MHz to 30 MHz, the measurement value slightly changes depend on the loading capacitance value, and the deviation increases when the frequency is greater than 10 MHz. The disturbances from telecommunications equipment were measured to confirm the validity of the LCC-CVP. The results indicated that the measurement results were almost the same as the results using impedance stabilization network (ISN) when the sufficient large capacitance was used as the loading capacitance.