Compensation for instrument losses in circuits containing a wattmeter, voltmeter, and ammeter

THE relative location, in a circuit, of a wattmeter, voltmeter, and ammeter generally requires careful consideration. If the voltmeter and wattmeter potential circuit are connected on the load side of the ammeter and wattmeter current coil, the potential circuits are subjected to the correct voltage, but the ammeter and wattmeter current is in error by the current through the potential circuits. On the other hand, connecting the voltmeter and wattmeter potential coil to the line side of the ammeter and wattmeter current coil permits the correct load current to flow through the instruments, but the potential-circuit voltage is incorrect by the voltage drop in the ammeter and wattmeter current coil.