What are ghost voltages on dual-impedance digital multimeters, and where do they occur?
Ø False voltage comes from electrified circuits and unpowered wires that are very close to each other (such as in the same conduit or trunking). This situation can form a capacitor, which will generate capacitive coupling between the energized wire and adjacent unused wires.
Ø When the wire of a multimeter is placed between an open circuit and a neutral conductor, a complete circuit is effectively formed through the input of the multimeter. The capacitance between the connected thermal conductor and floating conductor is combined with the input impedance of the multimeter to form a voltage divider. The multimeter then measures and displays the obtained voltage value. Most digital multimeters today have a sufficiently high input impedance to display this capacitive coupling voltage (thus giving the false impression that the conductor is charged). The multimeter actually measures the voltage coupled to the disconnected conductor. But sometimes, these voltages can reach 8085% of the "hard wired" voltage. If they are not identified as false voltages, it will consume additional time, effort, and funds in troubleshooting circuit issues
Ø The locations where false voltage is often encountered are the blown fuses in the distribution panel, unused cables or wires in the existing conduit, and the ground or neutral wires that are disconnected in the 1-V branch circuit or the card box that uses a 1-V control circuit to control the assembly line or transport function. A certain amount of false voltage can couple from the live side of the blown fuse to the open side. When constructing facilities or buildings and conducting electrical wiring, electricians often pass additional wires through conduit for future use. These wires usually remain unconnected before use, but capacitive coupling may occur. For control circuits, the location of the circuit is usually close to unused control lines, resulting in a false voltage.
