Clever Uses of Ordinary Multimeters
To distinguish between the live and neutral wires of a mains power supply, a test pen is generally used. If you currently do not have a test pen on hand but have a multimeter, you can also use a multimeter to identify the live and neutral wires of the mains power supply. The method is as follows: turn the conversion switch of the multimeter to AC 250V or 500V, connect one probe to the power supply, and connect the other probe to the ground (in a water pipe or damp place); When the reading of the multimeter approaches 220V, the measured point is the phase line; If the hands of the multimeter do not move and the conversion switch of the multimeter is gradually reduced to the lowest gear, and there is still no obvious reading, then the measured point is the zero line. If there is no grounding, the following method can be used: turn the conversion switch of the multimeter to the AC voltage range, connect any probe to the tested point of the power supply, pinch the other probe with the index finger and thumb, and if the multimeter reads. The measured point is the live line; If the pointer of the multimeter does not move, it is the neutral or ground wire.
When using this method, it should be noted that a multimeter is used to identify the live and neutral wires of the mains power. When the AC voltage level used by the multimeter is low, the test effect is obvious because the current flowing through the human body is high at this time. Sometimes there may be a feeling of numbness. On the contrary, when the AC voltage level used by a multimeter is high, the current flowing through the human body is smaller and safer; But sometimes the test results are not very obvious. Therefore, when using this method to distinguish between the live and neutral wires of the mains power, its testing effectiveness and safety are related to the insulation resistance of the operator's fingers, the humidity of the ground, and the internal resistance values of different models of multimeters in the AC voltage range. It should be flexibly mastered through practice. For the first time using this method, for safety reasons, when selecting the AC voltage range, it is recommended to shift from high to low to achieve a clear test effect.
