Improvement of measurement accuracy for Capacitive Voltage Probe without pre-calibration

Capacitive Voltage Probe (CVP) is used for measuring disturbances at telecommunication ports. The sensitivity of CVP changes by type of cable. Therefore, the pre-calibration is needed for every type of cable before measurement. The method of changing the input capacitance was proposed in order to avoid the pre-calibration. However, the accuracy of sensitivity was not sufficient. This paper proposes the method of improving the accuracy. The input capacitance was changed by a mechanical relay, and the output level difference was measured by a network analyser or a lock-in amplifier. The regression line parameters were obtained from the investigation which used many type of cable. The investigation showed that the deviation between the estimation value using the regression line and the measurement value is within 1dB. By using actual equipment, the disturbance level was measured and they were compared to the measured value by ISN. The results showed that the average deviation was within 1dB.