1. The formula for judging alternating current and direct current: the electric pen determines the alternating current and direct current, the alternating current is bright and the direct current is dark, the alternating current neon tube is bright, and the direct current neon tube is bright-end.
Explanation: First inform the reader - point, before using the low-voltage test pen, it must be tested on the confirmed charged body; it should not be used until the test pen is confirmed to be normal. When distinguishing between AC and DC, it is best to compare the two, so that it is obvious. When measuring AC, both ends of the neon tube light up at the same time, and when measuring DC, only one end of the neon tube is extremely bright.
2. The formula for judging the positive and negative poles of direct current: the electric pen determines the positive and negative poles, observe the neon tube carefully, the front end is bright and the negative pole is bright, and the back end is bright as the positive pole.
It is 110V and above; if people and the earth are insulated, - touch one pole of the power supply with one hand, and the other - only hold a test pen. It is the negative pole; if the back end of the neon tube is extremely bright, the power supply to be detected is the positive pole, which is based on the principle of unidirectional DC flow and the flow of electrons from the negative pole to the positive pole.
3. The formula for determining whether the DC power supply is grounded or not and the difference between positive and negative grounding: the DC coefficient of the substation, the electric pen does not light up; if it is bright near the tip of the pen, the positive pole has a ground fault; if it is close to the finger end, the ground fault is in the negative pole.
Note: The DC coefficient of power plants and substations is insulated from the ground. People stand on the ground and touch the positive or negative pole with an electroscope. The neon tube should not light up. If it lights up, it means that the DC system has Grounding phenomenon; if the light is on the end near the tip of the pen, it is the positive ground; if the light is on the end near the finger, it is the negative ground.
4. Judgment of in-phase and out-of-phase formulas: to determine whether two lines are the same or different, hold a pen in each hand, isolate the two feet from the ground, touch an important line with each of the two pens, watch with your eyes - a pen, if the same phase is not illuminated, it is different. .
Note: During this test, remember that the feet and the ground must be insulated. Because most of our country is powered by 380/220V, and transformers generally use the neutral point to be directly grounded, so during the test, the human body and the ground must be insulated to avoid forming a loop to avoid misjudgment; during the test, the two strokes are bright and not. The display is bright, so just look at one.
