What is the working principle of the electric pen
The principle of the electric pen to detect the light 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 if it is lower than a certain value, it will not emit light. The voltage measurement range of ordinary low-voltage electroscope pens is generally 60--500v, and the neon bulb may not emit light if it is lower than 60v. When it is higher than 500V, it cannot be tested with a low-voltage electroscope pen, otherwise insulation breakdown will occur, causing the danger of electric shock to the human body.
When holding an electric pen and standing on a stool or other insulators to test the live wire, the large current will pass through the large resistance drop-down resistance rod inside the electric pen to become a weak small current, and then pass through the neon bulb and the human body to discharge the surrounding environment. At this time, Neon bubbles will glow. However, there is no risk of electric shock to the human body at this time.
Somewhere in the neutral line is broken, why does the neon tube of the test pen glow?
Because the zero wire is short-circuited but the live wire is connected, the charged body, the test pen, the human body and the earth form a circuit when measuring electricity, so the neon bulb in the test pen will glow. When measuring the live wire, there is a voltage U=220V between the live wire and the ground, and the resistance of the human body is generally very small.
Usually only a few hundred to a few thousand ohms, and the internal resistance of the test pen is usually about a few megohms. The current passing through the test pen is very small, usually less than 1 milliampere. When such a small current passes through the human body, it will not harm people. And when such a small current passes through the neon bulb of the test pen, the neon bulb will emit light.
The function of the test pen:
Function 1: Electricity test, touch the object with the metal head, the object will be charged if it emits light, and it will not be charged if it does not emit light.
Function 2: It can be used for low-voltage phase verification to measure whether any wires in the line are in phase or out of phase.
Function 3: It can be used to distinguish between alternating current and direct current. When testing with a test pen, if both poles in the neon bulb of the test pen glow, it is alternating current; if only one of the two poles glows, it is direct current.
Function 4: It can judge the positive and negative poles of direct current. Connect the test pen to the DC circuit for testing, the pole that glows on the neon bulb is the negative pole, and the pole that does not shine is the positive pole.
Function 5: It can be used to judge whether the DC is grounded or not. In the ground-insulated DC system, you can stand on the ground and touch the positive or negative pole of the DC system with the test pen. If the neon bulb of the test pen does not light up, there is no grounding phenomenon. If the neon bulb lights up, it means that there is a grounding phenomenon, and if it lights up like it is on the tip of the pen, it means that the positive electrode is grounded. If the light is on the finger end, it is the negative ground.
