5 uses of the electric test pencil
1. To judge whether the object is charged. Its internal structure is - a light bulb with only two electrodes, and the bulb is filled with neon gas, commonly known as a neon bulb. One pole of it is connected to the tip, and the other pole is connected in series with a high resistance to the other end of the pen. When the voltage between the two poles of the neon bulb reaches a certain value, a glow will be generated between the two poles, and the intensity of the glow is proportional to the voltage between the two poles. When the voltage of the charged body to the ground is greater than the initial glow voltage of the neon bulb, and the tip of the test pen touches it, the other end is grounded through the human body, so the test pen will emit light. The function of the resistance in the test pencil is to limit the current flowing through the human body to avoid danger.
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. The specific method is: stand on an object that is insulated from the earth, hold a testing pencil in both hands, and then test on the two wires to be tested. If the two testing pencils glow brightly, the two wires are different. On the contrary, it is the same phase, which is judged by the principle that the voltage difference between the two poles of the neon bulb in the test pen is proportional to its luminous intensity.
3. It can be used to distinguish between alternating current and direct current. When testing with a test pen, if both poles in the bulb of the test pen emit light, it is alternating current; if only one of the two poles glows, it is direct current.
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 from the neon bulb is the positive pole, and the pole that does not shine is the negative pole.
5. It can be used to judge whether the DC is grounded or not. In the DC system that is insulated from the ground, 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 air bubble is bright, it means that there is a grounding phenomenon, and if the light 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. But it must be pointed out that in a DC system with a ground monitoring relay, this method can be used to judge whether the DC system is grounded.
