NPLC工频周期数
NPLC是采样电源的周期倍数，N代表是多少倍，PLC与采样电源有关
交流电源的干扰是很厉害的。为了减少交流电源的干扰，一个常用的方法就是把测量周期尽可能的取成交流周波的整数倍，这样，在一个周期内各种干扰能够互相抵消。我国用的交流电是50Hz，一个周期是0.02秒，因此若NPLC=1就是测量采样周期为0.02秒，若NPLC=10就是测量采样周期为0.2秒，若NPLC=50就是测量采样周期为1秒。只有这样才能抑制噪音，提高交流共模抑制比。当然，有的时候要追求测量速度，采样周期小于0.02秒，那必然要牺牲性能了。
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.
