Abstract: Isolated capacitance line voltage sensing is provided that avoids metal-to-metal contact for voltage sensing of a power signal present on a power wire. An external conductor is positioned by the power wire, creating a capacitor with the power wire conductor, insulation, and external conductor. The capacitance is used to measure the electric field, indicating a voltage level for the powered wire. The impedance mismatch caused by the capacitance is transformed. The impedance transformation circuit may be integrated with the external conductor, allowing voltage sensing by a voltage meter having a lower input impedance. A manual or automatic calibration circuit may be provided to ensure the measured voltage represents the actual voltage on the power wire.

Abstract: Isolated capacitance line voltage sensing is provided that avoids metal-to-metal contact for voltage sensing of a power signal present on a power wire. An external conductor is positioned by the power wire, creating a capacitor with the power wire conductor, insulation, and external conductor. The capacitance is used to measure the electric field, indicating a voltage level for the powered wire. The impedance mismatch caused by the capacitance is transformed. The impedance transformation circuit may be integrated with the external conductor, allowing voltage sensing by a voltage meter having a lower input impedance. A manual or automatic calibration circuit may be provided to ensure the measured voltage represents the actual voltage on the power wire.