1, immediate measurement method

General test pens can display information of 12v, 36v, 55v, 110v and 220v. In general, the final display information mark value of the display is the measured voltage value.

Immediate measurement method (220v voltage)

2, magnetic induction measurement method

The principle of detecting luminescence by electric pen is that there is a certain potential difference between the charged body and the earth. When the potential difference exceeds a certain value, the neon bulb will emit light, and below a certain value, it will not emit light. The voltage measurement range of ordinary low-voltage test pens is generally 60-500 V, and neon bulbs below 60v may not emit light. When it is higher than 500V, it can't be tested with a low-voltage test pen, otherwise insulation breakdown will occur, causing the danger of electric shock to human body.

When the hand-held electric pen stands on a stool or other insulators to test the fire line, the large current will turn into a weak small current through the large resistance step-down resistor rod inside the electric pen, and then discharge to the surrounding environment through the neon bubble and the human body. At this time, the neon bubble will emit light. However, there is no danger of electric shock at this time.