Patent ID: 8843334

Claim:
A variable power load detector apparatus, for use in a non-intrusive electrical load meter for metering the use of electricity supplied to a plurality of loads, the electricity supply providing an alternating voltage supply and an electrical current supply, the apparatus comprising: an input section arranged to receive values representative of the total instantaneous supply of at least one of electrical current and power to the plurality of loads as a function of time from the alternating voltage supply, the received values comprising a set of waveform values representative of a cyclic waveform of at least one of the electrical current and power supply, the total instantaneous supply of at least one of electrical current and power to the plurality of loads having been received without direct access to the plurality of loads; a delta waveform generator arranged to calculate a difference between a cyclic waveform and an earlier cyclic waveform, by subtracting the respective sets of waveform values, to obtain a delta waveform; an edge detector arranged to detect an edge or edges in the delta waveform; and an analysis section arranged to identify at least one load based at least on information on the edge or edges detected by the edge detector.