Non-contact long range AC voltage measurement

Safety requirements and physical constraints often prohibit contacting high voltage terminals. This limits the options for monitoring and maintaining high voltage machinery and power distribution grids. We present a non-contact AC (alternating current) voltage and frequency measurement system with 600 mm of operation range to overcome this issue. The method relies on measuring the electric potential of an AC voltage source using a single capacitive electrometer. Simultaneously, the distance from the AC source is measured using time-of-flight sensors. By combining the data from both sensors, AC voltages can be measured accurately without the need for any galvanic contact. The system is packaged in a handheld battery powered form factor. Measurements of voltages between 25 VRMS and 250 VRMS and distances from 25 mm to 600 mm demonstrated accuracy within 4%. Furthermore, frequencies between 5 Hz to 500 Hz were measured with 10 mHz of resolution. The presented technique can be used as a test and measurement instrument where the source terminals are inaccessible or as a wearable safety device in high-voltage environments.