They feared some undetected trace of poison.

他们担心一些识破的投毒痕迹。

This heating helps to break down weak spots in the dielectric that otherwise might pass through the electrode undetected, only to fail during a later spark or hipot test.

这热量帮助击穿电较薄的地方﹐否则材通过电极而没有检测到﹐结果在以后的火花测试和高压试验将会失效。