| 摘要 |
K samples of L successive cycles of an electrical signal that is at least approximately periodic are taken, where K = LN + D, to cause corresponding samples of successive cycles to unidirectionally drift. The value of N defines the number of samples per waveform cycle, the value of D is related to drift sampling rate. Unidirectional sampling drift ensures that all points on the signal wave form over a number of cycles are sampled to avoid missing a periodic waveform characteristic that might tend to occur between samples. Since the sampling rate is synchronized to L cycles of the input signal, the number of samples per cycle of the input signal is substantially constant as a function of input signal frequency. Quasi-asynchronous sampling in accordance with the invention is particularly useful for making electrical power line measurements in environments where power line frequency tends to vary. |
