Introduction to the electric pen's operation and uses
The electric test pen is one of the tools often used by electricians to determine whether an object is charged or not. Its internal structure is a light bulb with two electrodes. The bulb is filled with neon gas, commonly known as neon bulb. One pole of it is connected to the tip of the pen, and the other pole 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 the neon bulb reaches a certain value, a glow will be generated between the two poles, and the intensity of the 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 bulb, and the tip of the test pen touches it, the other end is grounded through the human body, so the test pen will emit light. The function of the resistance in the test pencil is to limit the current flowing through the human body to avoid danger.
In addition to judging whether the object is charged or not, the electric test pen also has the following uses:
(1) It can be used for low-voltage phase verification to measure whether any wires in the line are in phase or out of phase. The specific method is: stand on an object insulated from the earth, hold a test lead in each hand, and then test on the two wires to be tested. If the two test leads glow brightly, the two lead wires are different. On the contrary, it is the same phase, which is judged by the principle that the voltage difference between the two poles of the neon bulb in the test pen is proportional to its luminous intensity.
(2) It can be used to distinguish between alternating current and direct current. When testing with a test pen, if both poles in the neon bulb of the test pen glow, it is alternating current; if only one of the two poles glows, it is direct current.
(3) It can judge the positive and negative poles of direct current. Connect the test pen to the DC circuit for testing, the pole that glows on the neon bulb is the negative pole, and the pole that does not shine is the positive pole.
(4) It can be used to judge whether the DC is grounded or not. In the ground-insulated DC system, you can stand on the ground and touch the positive or negative pole of the DC system with the test pen. If the neon bulb of the test pen does not light up, there is no grounding phenomenon. If the neon bulb lights up, it means that there is a grounding phenomenon, and if it lights up like it is on the tip of the pen, it means that the positive electrode is grounded. If the light is on the finger end, it is the negative ground. However, it must be pointed out that in a DC system with a ground monitoring relay, this method cannot be used to determine whether the DC system is grounded.
