What are the functions of the testing pen
Measure if there is voltage in the circuit
This is the most commonly used function of a test pen, which is to hold the pen in the correct position and touch the conductor with the tip of the pen. If the electric pen lights up, it indicates the presence of voltage in the circuit. If the light is not on, it indicates that there is no voltage in the circuit.
But in practical use, it should be noted that the circuit's normal status cannot be judged solely by the light on or off of the electric pen. For example, neither a normal zero wire nor a short-circuit zero wire in an unused state can light up the pen, but the former is a normal phenomenon and the latter is a fault. For example, both a normal live wire and a misaligned zero wire can light up the pen, but the former is a normal phenomenon, while the latter is a fault.
Measure the in-phase or out of phase of the phase line
Circuits without distinguishing line colors can definitely cause headaches during maintenance. The single-phase circuit is fine, but if you encounter a three-phase circuit, it's really a big deal!
However, an electric pen has a magical function that can easily help you measure the in-phase or out of phase of phase lines.
When measuring, hold an electric pen in both hands and stand on an insulated object. Touch two electric pens simultaneously on two wires. If the brightness of both pens is low, it indicates that the two wires measured at this time are in phase (both are phase lines). If the brightness of two electric pens is high, it indicates that the two lines measured at this time are out of phase (one phase line and one neutral line).
By using this method, three phase lines and one neutral line in a three-phase circuit can be quickly screened out.
Distinguishing between AC and DC
Firstly, in terms of brightness, when measuring AC power with an electric pen, the brightness should be significantly higher than that of DC power.
Secondly, it is distinguished from the position of the brightness of the electric pen. The luminescent body of an electric pen, called a neon tube, is in the shape of a long strip. When measuring alternating current, the entire neon tube emits light; When measuring direct current, only one end of the neon tube emits light.
Measure the positive and negative poles of direct current
In the previous paragraph, we mentioned that when measuring direct current, only one end of the neon tube lights up. At this point, the position of the neon tube can be used to determine the positive and negative poles of the power supply.
When measuring the positive pole of the power supply, the end of the neon tube near the pen tip lights up; When measuring the negative pole of the power supply, the end of the neon tube that is away from the pen tip lights up.
