高压ns脉冲测量中的分压器性能及阻抗匹配

为研究ns级高压脉冲测量中存在的问题,探讨了分压器阶跃响应性能与脉冲测量结果的关系及测量系统的阻抗匹配与否对测量结果的影响。由阶跃响应性能不同的分压器的双指数脉冲响应的Pspice仿真和实验测量可知:当分压器阶跃响应存在过冲时,波形上升和下降时间变短;当阶跃响应的上升时间大于被测双指数脉冲的上升时间时,波形上升和下降时间加长。基于传输线理论和Pspice仿真分析及实验测量结果可知:系统内部阻抗不匹配将导致反射和初始分压比小于稳态分压比,高压引线始端不匹配将激发振荡。因此,只有当分压器的阶跃响应无过冲且上升时间低于被测脉冲上升时间、测量系统的阻抗匹配时,才可能得到准确的测量结果。

Performance and Impedance Match of Divider in High Voltage Nanosecond Pulse Measurement

The relation between the results of pulse measurement and the performance of resistance divider step response was discussed in this paper. It was showed that different performances of divider step response causes different measurement results by Pspice simulation and measurement . The rise time and fall time of measuring results are both elongated when the rise time of a divider step response is longer than the rise time of exp-pulse wave. The measured results show that the rise time and fall time are both shorter when divider step response has overshoot distortion and its rise time is not longer than the rise time of wave. It is revealed that impedance mismatching of measurement system influences the result of high voltage nanosecond pulse measurement in this paper. Some results are gained based on theoretical analyses of transmission line and Pspice simulation and test measurement. The beginning divider ratio is less than that in steady state when the impedances between cable and digitizing storage oscilloscope are not matched. The reflected wave is caused and could join to measurement result when those impedances are mismatched both in cable front end and terminal. The position of reflected wave adding is related to the length of cable. The reflected wave can not be added when the cable is long enough. Surge would be stirred if the front end of high voltage down-lead between pulse generator and divider is impedance mismatched. And the wave period of surge is longer and longer with the length of down-lead. The conclusion is showed as follows. For achieving precision measurement, the step response rise time of divider must be less than the rise time of pulse waiting for being measured and has no any overshoot, and measurement system must be impedance matched.