A voltage probe for measuring voltage on a mechanical device. The voltage probe includes a sensing brush, a grounding brush, a grounding switch, and an electronic processor. The electronic processor is configured to receive a voltage from the sensing brush and, after a change of state of the grounding switch, which electrically connects the grounding brush to a mechanical device, measure voltage on the mechanical device, compare the measured voltage to a predetermined threshold, and generate an electronic signal indicative of the measured voltage or the comparison.