Patent ID: 7756651

Claim:
A method of sampling a power line signal, comprising: selecting a first sample of a power line signal; determining a portion of the first sample that belongs to a first line cycle; and selecting a second sample of the power line signal; determining a portion of the second sample that belongs to the first line cycle; adding the portion of the first sample and the portion of the second sample; determining a frequency of interest of the power line signal, wherein the frequency of interest is at least one of the following: a nominal frequency, a harmonic of the nominal frequency, a tolerance frequency or a harmonic of the tolerance frequency, and wherein the nominal frequency is a standard power line signal frequency and the tolerance frequency differs from the nominal frequency; and calculating quantities of the power line signal for the frequency of interest including at least one of the following: total harmonic distortion, magnitudes of components within a signal of a particular frequency, angles of a frequency signal with respect to another signal, or harmonic energy.