Patent ID: 7079961

Claim:
A method for accurately measuring the real and reactive power of a system or component at a predetermined line frequency, comprising the steps of: providing a measurement channel and an additional measurement channel and setting a source coupled to a device under test in the measurement channel to zero; measuring an interference signal n (t) on the measurement channel and measuring an interference signal n′ (t) on the additional measurement channel; calculating a phase ratio and an amplitude ratio between the interference signal n (t) and the interference signal n′ (t) ; setting the source to a desired voltage and frequency value and measuring a voltage v(t) and current i MEAS (T) signal on the measurement channel, and measuring an interference signal n′ (t) on the additional measurement channel, wherein the measured interference signal n′ (t) is adjusted by the phase and amplitude ratio and is continuously subtracted from the i MEAS (T) signal; and calculating at least one of a real and reactive power, loss angle, and power factor of the device under test using the measured v(t) and adjusted i MEAS (T) signal.