5 ways to use the test pencil
1. Judgment formula for alternating current and direct current: electric pen judges alternating current and direct current, alternating current is bright and direct current is dark, the whole body of the alternating current neon tube is bright, and one end of the direct current neon tube is bright.
Explanation: First of all, let the readers know that before using the low-voltage tester, it must be tested on the confirmed electrified body; before the tester is confirmed to be normal, it must not be used. When distinguishing AC and DC, it is best to make a comparison between the "two powers", so that it is obvious. When measuring alternating current, both ends of the neon tube are illuminated at the same time, and only one end of the neon tube is extremely bright when measuring direct current.
2. The formula for judging the positive and negative poles of direct current: judge the positive and negative poles with the electric pen, and observe the neon tube carefully.
Note: The front end of the neon tube refers to the end of the test pen tip, the back end of the neon tube refers to the end held by the hand, the bright front end is the negative pole, and the opposite is the positive pole. When testing, pay attention: the power supply voltage is 110V and above; if the person is insulated from the ground, touch any pole of the power supply with one hand, and hold the test pencil with the other hand. If the back end of the neon tube is bright, the tested power supply is positive, which is based on the principle of DC unidirectional flow and electron negative to positive flow.
3. The formula for judging whether the DC power supply is grounded or not and the grounding of the positive and negative poles: the DC coefficient of the substation, the electric pen does not light up; if the light is close to the tip of the pen, there is a ground fault on the positive pole; if the light is close to the finger end, the ground fault is on the negative pole.
Explanation: The DC coefficients of power plants and substations are insulated from the ground. If a person stands on the ground and touches the positive or negative poles with a test pen, the neon tube should not be lit. If it is lit, it means that the DC system has problems. Grounding phenomenon; if the light is on the end near the tip of the pen, it is the positive ground; if it is on the end near the finger, it is the negative ground.
4. Judgment of the same phase and different phase formula: To determine whether two lines are the same or different, hold a brush in each hand, with both feet insulated from the ground, touch a main line with each of the two brushes, and look at a pen with your eyes.
Note: During this test, remember that the two feet must be insulated from the ground. Because most of our country is powered by 380/220V, the neutral point is generally used for direct grounding of transformers, so when testing, the human body and the earth must be insulated to avoid forming a loop to avoid misjudgment; when testing, the two pens are bright and not The bright display is the same, so you can only look at one.
5. Judgment formula for phase wire grounding fault of 380/220V three-phase three-wire system power supply line: three-phase wire connected in shape, two wires are bright when touched by the electric pen, and the brightness of the remaining wire is weak, and the phase wire is grounded; if there is almost no light, it is ground fault Fault.
Explanation: The secondary side of the voltage booster is generally connected in a Y shape. In a three-phase three-wire system where the neutral point is not grounded, when the three phase wires are touched with an electroscope, two of them are slightly brighter than usual, while the other If the brightness on the root is weaker, it means that the phase line with weak brightness is grounded, but it is not too serious; if two are very bright, and the remaining one is almost invisible, it means that the phase line has a metal grounding. Fault.
