How does a multimeter distinguish between fire and zero wires?
I think there are several ways:
1. multimeter to AC voltage gear to the largest gear, with one hand pinch a pen needle, the other pen connected to the wire you want to measure. High voltage for the fire wire, low voltage for the zero line.
With this method of judgement, measured out of the firewire has tens to one or two hundred volts voltage varies. But the actual voltage is normal, because the human body + shoes have resistance, so the measured voltage will be low. Specifically how much is related to the shoes and the size of the grounding resistance.
Note: It is necessary to ensure that the voltage file, if the resistance or current file with this method will be electrocuted!
2. multimeter hit to AC voltage file 750V or 250V file, a pen ground or distribution cabinet shell (distribution cabinet shell are generally grounded), another pen connected to the measured wire. Firewire measured out about 220V voltage; zero line measured out the voltage is very low, close to zero.
In the practical application of electricians, the measurement of the distribution cabinet phase voltage are generally used in this way, this method of measuring out the results are accurate and reliable.
3. multimeter to AC voltage file 750V or 250V file. Put a meter pen line in the finger wrapped around a few times, the needle is suspended without contacting anything; the other pen touching the measured wire, if the multimeter shows a certain voltage for the firewire, does not show for the zero line. This method is not very reliable, sometimes there will be a misjudgement.
Multimeter, also known as multipurpose meter, multi-purpose meter, triple meter, complicated meter, etc., is an indispensable measuring instrument for power electronics and other departments, generally to measure voltage, current and resistance as the main purpose. Multimeter is divided into pointer multimeter and digital multimeter according to the display mode. It is a multifunctional, multi-range measuring instrument, generally the multimeter can measure DC current, DC voltage, AC current, AC voltage, resistance and audio level, etc. Some can also measure AC current, capacitance, inductance and some parameters of semiconductors (e.g., β) and so on.
