Dual capacitive sensors for non-contact AC voltage measurement

Non-contact voltage sensors are designed to detect the voltage in a wire or piece of equipment without actually making direct contact with the conductor or energized part. Conventional single capacitive probe approach is not accurate and could easily be affected by environmental factors. In this paper, a capacitive probe with two sensor heads has been developed for the accurate sensing of AC voltage. Orthogonal least squares estimation algorithm has been implemented to identify the nonlinear relationship between the two sensor heads readings and the sensed AC voltage. With the added second sensor head, the sensed AC voltage will be less sensitive to the medium of the sensing environment and distance between the sensing surface and the probe. Experimental results are included to show the effectiveness of the proposed sensor system with the fitted model in sensing different AC voltages under different sensing environments.