Patent ID: 8489351

Claim:
A method of calculating a frequency of a waveform having periodic cycles including a current cycle and a previous cycle, each cycle having four equally spaced phase angles, the waveform measured from a monitoring device, the method comprising: measuring a plurality of data points from a current cycle of the waveform via the monitoring device; referencing a last point of interest from the previous cycle of the waveform via a controller; determining four points of interest at equally spaced phase angles from the current cycle of the waveform by selecting a subset of the plurality of data points around each of the equally spaced phase angles and calculating the average of the subset of data points around each of the respective equally spaced phase angles of the current cycle of the waveform via the controller; subtracting the average value of the points of interest in the current cycle from the four points of interest and the last point of interest from the previous cycle to compensate for DC bias; and determining a frequency of the waveform based on the determined four points of interest of the current cycle and the last point of interest from the previous cycle.