Harmonic synthesis techniques extend capabilities of wattmeter calibrators for meter influence testing

Wattmeter calibrators such as the Rotek 800 family are used for basic calibration checks of both static watthour and rotating induction energy meters. They can also be used in a limited manner for influence testing, but are not capable of performing the full range of influence tests without recourse to constructing ancillary circuits. One particular area of difficulty is that of harmonic testing. The method described allows for the generation of harmonics without the complication of phase locking techniques and the associated stability problems, and for the calibration of meters under test in respect of their ability to resolve harmonic power. Also considered is the possibility of using direct digital synthesis as a means to produce waveforms with accurate harmonic content and the benefits of the inherent stability of a digital system