A device for measuring power, or other circuit parameters, of an alternating current load. The device has an ammeter and voltmeter for measuring voltage across the load and current through the load. The device also has a known impedance element that is switchably connected across the load. The ammeter is used to provide a second current measurement with the impedance so connected. These measurements, together with the known impedance value, are used to calculate power, the power factor, impedance, or some other parameter associated with the load. The same device may also be implemented circuitry that is the "dual" of that described above, such that voltage rather than current measurements are used.
Richard T. Smith