How many volts can the test pencil measure? The measuring range of the low-voltage electric pencil
How many volts can the test pencil measure? The measuring range of the low-voltage electric pencil
Low-voltage measuring pen: used for the detection of charged objects with a line voltage of 500V and below.
Weak current testing pen: used for testing electronic products, the general test voltage is 6v--24v. For ease of use, the tail of the electric pen often has a lead wire with a clip.
High-voltage measuring pen: used for 10kv and above projects, and is a daily testing tool for electricians.
The low-voltage electroscope pen is an auxiliary safety tool commonly used by electricians. It is used to check whether the conductor below 500V or the shell of various electrical equipment is charged. An ordinary low-voltage electroscope pen can be carried with you. As long as you master the principle of the electroscope pen and combine it with the well-known electrical principles, you can use it flexibly.
steps/methods
(1) Judgment of alternating current and direct current
The electric pen judges AC and DC, AC is bright and DC is dark,
The whole body of the AC neon tube is bright, and one end of the DC neon tube is bright.
illustrate:
First of all, let the readers know that before using the low-voltage electrometer pen, it must be tested on the confirmed electrified body; it must not be used until it is confirmed that the electrometer pen is normal. 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 light up at the same time, and when measuring direct current, only one end of the neon tube is extremely bright.
(2) The formula for judging the positive and negative poles of direct current:
Use the electric pen to judge the positive and negative poles, and observe the neon tube carefully.
The bright front end is the negative pole, and the bright rear end is the positive pole.
illustrate:
The front end of the neon tube refers to the tip of the electroscope pen, and the back end of the neon tube refers to the end of the hand. The bright front end is the negative pole, and the opposite is the positive pole. Attention should be paid when testing: the power supply voltage is 110V and above; if the person is insulated from the ground, one hand touches any pole of the power supply, and the other hand holds a measuring pen, the metal head of the pen touches the other pole of the power supply under test, and the front end of the neon tube If the back end of the neon tube is bright, the power supply being tested is positive, which is based on the DC unidirectional The principle of flow and electron flow from the negative electrode to the positive electrode.
(3) Judging 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 when touched;
If the light is close to the tip of the pen, there is a ground fault at the positive pole;
If the light is close to the finger end, the ground fault is at the negative pole.
illustrate:
The DC coefficients of power plants and substations are insulated from the ground. When a person stands on the ground and touches the positive or negative pole with a test pen, the neon tube should not light up. If it lights up, it means that the DC system is grounded. ; 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) Formulas for judging the in-phase and out-of-phase formulas
To judge the sameness and difference between two lines, hold a pen in each hand,
The two feet are insulated from the ground, and each of the two pens touches a main line.
Look at a pen with your eyes, if it is not bright, it will be different if it is bright.
illustrate:
During this test, remember that the two feet must be insulated from the ground. Because most of our country is powered by 380/220V, and the neutral point of the transformer is generally grounded directly, so when doing the test, the human body must be insulated from the earth to avoid forming a loop, so as to avoid misjudgment; The bright display is the same, so only one can be seen.
(5) Judgment formula for phase wire ground fault of 380/220V three-phase three-wire power supply line
The three-phase line of the star connection method, the electric pen touches two lights,
The brightness of the remaining one is weak, and the phase wire is grounded;
If there is almost no light, there is a metal ground fault.
illustrate:
The secondary side of the power transformer 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 brightness of the other is brighter. If it is weaker, it means that the phase line with weak brightness has a grounding phenomenon, but it is not too serious; if two are very bright, and the remaining one is almost invisible, it means that this phase line has a metal ground fault.
