type
According to the measured voltage is divided into:
High-voltage measuring pen: used for 10kv and above engineering operations, and it is a daily test tool for electricians;
Low-voltage measuring pen: used to detect charged objects with line voltage of 500V and below.
Weak current pen: used to test electronic products, with a general test voltage of 6v-24v. In order to facilitate the use, the tail of the electric pen often has a lead with a clip.
According to contact information
Contact electric probe: a detection tool that obtains electrical signals by contacting charged objects. Usually the shape is a screwdriver, which is used for both electric pens and screwdriver. Pen-type, display measurement data directly in LCD window.
Inductive electric probe: Inductive test can be used to detect the voltage on the control line, conductor and socket or detect the open circuit position along the conductor without physical contact. The personal safety of testers can be ensured to a great extent.
Two uses
In addition to judging whether an object is charged, pencils can also be used for the following purposes:
(1) can be used for low-voltage nuclear phase detection to measure whether any wires in the line are in-phase or out-of-phase. The specific method is as follows: stand on an object insulated from the earth, hold a stylus in each hand, and then test on two wires to be tested. If two styluses emit bright light, the two wires are out of phase; On the other hand, it is in phase, which is judged by the principle that the voltage difference between the two poles of neon lamp bulb in the test pen is proportional to its luminous intensity.
(2) It can be used to distinguish alternating current from direct current. When testing with a pencil, if both poles in the neon lamp of the pencil shine, it is alternating current; If only one of the two poles emits light, it is direct current.
(3) The positive and negative poles of direct current can be judged. Connect the measuring pen to the DC circuit for testing. The bright pole of a neon bulb is the negative pole, and the unlit pole is the positive pole.
(4) It can be used to judge whether DC is grounded. In a DC system insulated from the ground, you can stand on the ground and touch the positive or negative pole of the DC system with a stylus. If the neon light of the stylus is not on, there is no grounding phenomenon. If the neon light bulb lights up, it means that there is grounding phenomenon. If the pen tip lights up, it means that the positive electrode is grounded. If it shines on the finger end, it is the negative electrode grounded. However, it must be pointed out that this method can not be used to judge whether the DC system is grounded in the DC system with grounding monitoring relay.
Measuring pen is one of the tools commonly used by electricians to judge whether an object is charged or not. Its internal structure is a light bulb with only two electrodes, which is filled with neon gas, commonly known as neon lamp. One electrode of the bulb is connected to the pen tip, and the other electrode is connected to the other end of the pen after a high resistance is connected in series. When the voltage between the two poles of neon lamp bulb reaches a certain value, glow will be generated between the two poles, and the intensity of 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 lamp, when the tip of the stylus touches it, the other end is grounded through the human body, so the stylus will emit light. The function of the resistor in the test pen is to limit the current flowing through the human body and avoid danger.
3 correct use
(1) Determine AC and DC formulas The stylus determines AC and DC, AC is bright and DC is dark. The AC neon tube is on, and one end of the DC neon tube is on. Note: First of all, tell the reader that before using the low-voltage test pen, you must test on the confirmed charged body; Do not use the test pen until it is confirmed to be normal. It is obvious that when judging alternating current and direct current, it is best to make a comparison between the two. When measuring alternating current, both ends of the neon tube emit light at the same time, and when measuring direct current, only one end of the neon tube emits light.
(2) DC positive and negative judgment formula: the electric pen judges the positive and negative poles, and the neon tube should be carefully observed. The bright front end is the negative electrode, and the bright back end is the positive electrode. Description: the front end of neon tube refers to one end of the pen tip, and the back end of neon tube refers to the hand-held end. The bright front end is the negative electrode, otherwise it is the positive electrode. Attention should be paid to: the power supply voltage is 1 10V and above; If people are insulated from the earth, one hand touches any pole of the power supply and the other hand holds the stylus. The metal tip of the stylus touches the other pole of the power supply to be tested, the front end of the neon tube is extremely bright, and the power supply to be tested is the negative pole. If the back end of neon tube is extremely bright, the power supply to be contacted is the anode, which is based on the principle that DC flows in one direction and electrons flow from the cathode to the anode.
(3) Whether the DC power supply is grounded or not is judged. The difference between positive and negative grounding is the formula of the DC coefficient of the substation, and the pen will not emit light when touched; If the lamp is close to the pen tip, the positive electrode has a grounding fault; If the lamp is close to the finger end, the grounding fault is at the negative pole. Description: 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 be lit. If they are lit, it means that the DC system is grounded. If the light shines on the end close to the pen tip, the positive electrode is grounded; If the light shines on the end close to the finger, the negative electrode is grounded.
(4) The judgment formula of in-phase and out-of-phase determines that the two lines are the same and different. Hold a pen in each hand and insulate your feet from the ground. Every pen touches an important line. You can look at a pen with your eyes. It's different if it's not bright. Note: In this test, remember that your feet must be insulated from the ground. Because most of the power supply in China is 380/220V, transformers are generally directly grounded at neutral points, so it is necessary to insulate the human body from the earth during the test to avoid forming a loop and avoiding misjudgment; During the test, the two bright and unlit monitors are the same, just look at one.
(5) Determine the grounding fault of 380/220V three-phase three-wire power supply line. The pencil touches two lamps, and the remaining one is weak, and the phase line has been grounded; If there is almost no light, it is a fault of metal grounding. Note: The secondary side of power transformer is generally connected in Y-shape. In a three-phase three-wire system with ungrounded neutral point, when touching three phase wires with a test pen, two of them are slightly brighter than usual, while the brightness on the other one is weak, indicating that this phase wire with weak brightness is grounded, but it is not too serious; If two of them are bright and the other one is almost invisible, it is a metal grounding fault in this phase line.
4 Preventive measures
(1) Before using the electric probe, check whether there is a safety resistor in the electric probe, and then visually check whether the electric probe is damaged, damp or flooded. It can only be used after inspection.
(2) When using the electric pen, you can't touch the metal probe at the front end of the electric pen with your hands, which will cause personal electric shock accidents.
(3) When using the electric pen, be sure to touch the metal part at the end of the electric pen with your hand. Otherwise, because the charged body, the electric probe, the human body and the earth do not form a loop, the neon bubble in the electric probe will not emit light, which will lead to misjudgment and it is very dangerous to think that the charged body is not charged.
(4) Before measuring whether the electrical equipment is charged, it is necessary to find a known power supply to test whether the neon lamp in the electroprobe can emit light normally, and then use it.
(5) When testing a charged body under strong light, pay special attention to whether the neon bulb really glows (or not glows). If necessary, use the other hand to block the light and judge carefully. Don't misjudge, judge neon lights as non-luminous, and judge whether there is electricity or not.
5 chemistry
An electrician's necessity, a pen used to measure whether an object has electricity. The electric pen looks like a pen, ballpoint pen and screwdriver. Regardless of its appearance, its construction principle is basically the same: the shell is mostly plastic insulator, and the inside is composed of metal conductor, small bulb and resistance wire. The small bulb is filled with a colorless inert gas (neon), which can produce red light with strong transmittance under the excitation of electric field. When the object is charged, use an electric pen to test the redness of the neon light bulb, otherwise the neon light bulb will not light up.