答：PCIS开关可以控制并决定交流电流输入到负载上的相角，这在针对电容/有感负载电路的测试时是非常有用的，这样可以知道产生*大冲击电流时的相位角。PCIS开关连接在交流电源和负载中间，用扩展端口来连接PCIS，用辅助菜单栏目来编辑PCIS。
直流偏置选项的功能是：当外接电流互感器测量电流时会产生直流偏置误差，比如霍尔效应传感器，此时直流偏置功能可以用来抵消这种由外部互感器系统带来的直流偏置产生的误差。
Please see below answers to your questions;
1. The PCIS inrush switch provides the ability to decide upon which phase angle the AC source is applied to the DUT, this is particularly useful for capacitive/inductive load testing when known phase angles are to cause maximum inrush current. The PCIS is connected in-between the AC source and DUT, the extension port is used to communicate with the PCIS and the aux menu is used to program the switching of the PCIS.
2. The DC offset function is used when you are measuring current with an external CT that introduces a DC offset error into the measurement, such as a hall effect sensor. This can be “offset” with the DC offset function.