Performance and application of side electric pen
In daily maintenance work, whether it is to check and repair electrical circuits or various household electrical equipment, a small electric test pen is indeed an indispensable tool. It can conveniently and quickly help analyze many faults of various electrical appliances and equipment. Electric measuring pens can be divided into three types, namely, the most common low-voltage electric measuring pens for daily use, medium-voltage electric measuring pens for wells and mines, and high-voltage electric measuring pens for distribution stations. Although the three types of electric pens are applicable to different measurement voltage ranges, they Its working principle is basically the same.
The structure of the test pen is composed of a metal pen tip, a voltage limiting resistor, a neon tube, a spring, and a metal body at the end of the pen. Its working principle is quite simple. When the metal pen tip of the test pen contacts the live wire of the power supply, and the metal body at the end of the pen touches the human hand, the current returns to the power ground wire through the pen tip, resistor, neon tube, metal body at the pen tail, human body and the ground. , forming a complete current path, so the weak current limited by the resistor makes the neon tube glow. Since the current flowing through the human body is extremely weak, there will be no feeling of numbness when measuring a live conductor. Although the electric test pen is simple in structure and easy to use, if it is used incorrectly, it will often cause misjudgment. Therefore, it is necessary for beginners to understand how to use the electric test pen correctly.
(1) If the neon tube emits light when the handheld electric pen touches the charged object, it means that the object under test is charged. If the neon tube does not emit light after touching the conductor, it cannot be immediately determined that the conductor under test is not charged, because if the surface of the conductor is dirty with oil, etc., it will cause poor contact between the test pen and the conductor. It is best to rub the surface of the object under test with the tip of the electric pen repeatedly for several times. If the neon tube still does not emit light, it can be determined that the object under test is not charged.
(2) When using the electric test pen to judge whether the transmission line is in the same phase or out of phase, you can connect the two ends of the electric test pen to the insulated wires and touch the two line wires respectively, as long as the electric test pen does not touch other objects (including insulating objects) to make it suspended . When the electric probe is not in contact with other objects (including insulating objects), it is suspended in the air. When the electric measuring pen emits light, the two wires are out of phase, and when they are not in light, they are in phase.
(3) When using the test pen to test whether the circuit is AC or DC, if only one end of the neon tube of the test pen lights up, it means that there is DC power in the circuit under test; otherwise, if both ends of the neon tube light up at the same time, the circuit is AC.
(4) When it is necessary to judge the positive and negative poles of the DC circuit, you can touch the wire of the circuit under test with the electric test pen. The electrode that is bright on the neon tube is connected to the negative pole of DC, and the electrode that is not bright on the neon tube is connected to the DC current. positive electrode.
(5) When it is necessary to determine which electrode is grounded between the negative pole and the positive pole of the direct current, you can touch the measured point with the electric measuring pen. If the neon tube lights up, it means that one end of the direct current is grounded. The front end of the neon tube is bright, indicating that the positive pole of the circuit is grounded; the back end of the neon tube is grounded. The front end of the neon tube lights up, indicating that the positive pole of the circuit is grounded; the back end of the neon tube lights up, indicating that the negative pole is grounded.
(6) When the shell of electrical equipment has hemp inductance, and it is necessary to distinguish whether it is induction electricity or circuit leakage, you can use the electric measuring pen to touch the shell of the electrical equipment. If one or both ends of the neon tube emits a slight red light, it indicates that the shell of the electrical appliance is If you touch the shell with your hand at this time, the neon tube will go out; if the luminous brightness of the neon tube is very strong, if you touch the shell with your hand at this time, the neon tube will go out; if the luminous brightness of the neon tube is very strong.
