为了消除脉冲功率装置放电时地电位抬升对测试系统造成的影响，在测量探头和测量设备之间使用了共模电感。对等效电路进行了仿真分析，结果表明：对于探头输出的信号，该共模电感等效为传输线；对于共模信号等效为一个较大的电感，可以实现探头地电位隔离。共模电感使用绕制在磁芯上的同轴电缆制作，并进行了快脉冲信号传输和地电位隔离效果实验。实验结果与理论分析一致。该共模电感的响应时间为5.4 ns，隔离了约10 kV的脉冲高压，确保了示波器的安全运行。

When pulse power device discharge, the voltage to ground rises. It leads to a common mode current from probe’s ground to oscilloscope’s. The output waveform can be affected, and the oscilloscope can be destroyed sometimes. A common mode inductance(CM inductance) made by coaxial cable which enwinds a ferromagnetic core was designed between the probe and oscilloscope. The voltage to ground was calculated based on the equivalent circuit with inductance and resistance of grounded connector. The CM inductance reduced the common mode current and isolated the ground of probe to oscilloscope. The output voltage was measured using a square waveform source with the rise time of 4.8 ns, the rise time of CM inductance output is 7.2 ns. A circuit for testing the isolating impact was designed: The outer conductor of input cable to CM inductance is connected to 10 kV voltage pulse whose width is about 1.5 μs and the rise time is about 30 ns, the output cable of CM inductance is connected to the oscilloscope. The output voltage waveform of sample resistor transmitted through the CM inductance is in accord with the input, and the oscilloscope is safe．