Hvorfor lyser den ikke-kontaktbare testpennen når du tester deg selv

Hvorfor lyser testpennen uten-kontakt når du tester deg selv?

Because he works on batteries. The simple test pen has no battery and relies on the test source's own voltage to light up the light. The advanced test pen that can measure weak current or whether it is powered or not has a battery inside. It is similar to a current amplifier, and it can measure how weak the current is. Different according to the range.