Non-contact voltage measurement using electronically varying capacitance

A voltage measurement methodology is presented, based on the principle of a vibrating capacitance, but implemented electronically. A transconductor with time-varying gain synthesises the vibrating capacitance, the peak to peak charge current of which changes as different DC voltages are applied to the capacitively coupled input. This technique allows for the non-invasive measurement of DC voltages. Experimental results show that the amplitude of the output signal can indeed be used to determine input voltage, with the response being dependent upon the capacitance values in the circuit and the frequency of a locally applied signal that is independent of the voltage being measured. © 2010 The Institution of Engineering and Technology.