The purpose of measuring electric pens_ How to accurately use a measuring pen
A test pen is one of the commonly used tools by electricians to distinguish whether objects are charged or not. Its internal structure is a light bulb that only requires two electrodes, filled with neon gas, commonly known as a neon bubble. One pole is connected to the pen tip, and the other pole is connected in series with a high resistance wire to the other end of the pen. When the voltage between the north and south poles of a neon bubble reaches a certain value, a glow occurs between the north and south poles, and the intensity of the glow is proportional to the voltage between the north and south poles. When the voltage between the charged body and the ground is greater than the glow voltage at the beginning of the neon bubble, and the top end of the measuring pen is touched, the other end is grounded through the human body, so the measuring pen will emit light. The effect of measuring resistance in an electric pen is to bind the current flowing through the human body to avoid characteristic hazards.
In addition to being able to distinguish whether an object is electrified, a test pen also has the following uses:
(1) It can be used for low-voltage core phase measurement to determine whether any wires in a circuit are in phase or out of phase. The detailed method is to stand on an object insulated from the ground, hold a measuring pen in each hand, and then walk through the two wires to be tested for inspection. Assuming that the two measuring pens emit very bright light, then these two wires are out of phase; On the contrary, it is in phase, which is based on the principle that the voltage difference between the north and south poles of the neon bubble in the measuring pen is proportional to its luminous intensity.
(2) Can be used for differential communication between electricity and direct current. When using a stylus for verification, it is assumed that both poles in the neon bubble of the stylus emit light, indicating communication electricity; Assuming that only one of the two poles needs to emit light, it is a direct current.
(3) Capable of distinguishing between positive and negative electrodes of direct current. Connect the test pen to the DC circuit for verification. The electrode with the neon bubble shining is the negative electrode, and the electrode without the neon bubble shining is the positive electrode.
(4) Can be used to differentiate whether DC is grounded or not. In a DC system with insulation to ground, one can stand on the ground and touch the positive or negative pole of the DC system with a measuring pen. Assuming that the neon bubble of the measuring pen is not bright, there is no grounding phenomenon. Assuming that the neon bubble shines, it indicates a grounding phenomenon, and if it shines at the top of the pen, it indicates a positive grounding. If it shines on the finger end, it is negative grounding. However, it is necessary to point out that in DC systems with grounding monitoring relays, this method cannot be used to determine whether the DC system is grounded or not.
How to accurately use a measuring pen:
① Before checking whether the electrical appliances and circuits are live, you should first try them in a charged area to see if the test pen is intact, in order to prevent electric shock caused by differential errors.
② When holding the pen, press the tail of the measuring pen with your fingers, and hold the pen body with other fingers.
③ When measuring electricity, the pen tip touches the test body and the hand touches the tail of the measuring pen. Assuming that the test body is charged, the neon tube of the measuring pen will emit light; If the neon tube does not emit light, it indicates that the inspection body is not charged.
④ If the insulation resistance of the measuring pen is less than 1 megohm, it cannot be used.
