Aperture Time與NPLC

NPLC工頻週期數

NPLC是採樣電源的週期倍數，N表明是多少倍，PLC與採樣電源有關

交流電源的干擾是很厲害的。爲了減小交流電源的干擾，一個經常使用的方法就是把測量週期儘量的取成交流周波的整數倍，這樣，在一個週期內各類干擾可以互相抵消。我國用的交流電是50Hz，一個週期是0.02秒，所以若NPLC=1就是測量採樣週期爲0.02秒，若NPLC=10就是測量採樣週期爲0.2秒，若NPLC=50就是測量採樣週期爲1秒。只有這樣才能抑制噪音，提升交流共模抑制比。固然，有的時候要追求測量速度，採樣週期小於0.02秒，那必然要犧牲性能了。

NPLC is number of power line cycles.  DC Voltage, DC Current, and Resistance measurement resolution, accuracy is reduced by power line induced AC noise.  Using NPLC of 1 or greater increases AC noise integration time, and increases measurement resolution and accuracy, however the trade-off is slower measurement rates.  For highest measurement accuracy NPLC of 100 is recommended.