Use a multimeter to measure continuity
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We often encounter the situation of measuring continuity. When there is no voltage, we can easily use the continuity switch of the multimeter to measure； But when measuring the terminal voltage, for example a voltage of 220V, can I still directly measure continuity? Will it burn out the multimeter? If the voltage to ground at two points is measured separately, both are 220V, and sometimes it cannot be determined that both ends are in a conductive state.
In this case, I usually connect a resistor and measure the current.
When measuring the 220VAC voltage with the resistance setting of a multimeter, the multimeter will definitely burn out. You can connect a resistor as mentioned above to measure the current. You can also use a simpler method to connect a light bulb to determine whether the circuit is connected.
You can measure the voltage. Use the voltage setting to find the 220 live or neutral wire. Measure the voltage before and after the component you want to test enters the line. Make sure there is voltage when measuring the incoming line. Then, if there is voltage on the line, you will know whether it is connected or not. This post was last edited by faner on 2009-3-9 16:29 ]
I agree that when measuring the 220VAC voltage on the 5th floor with the resistance setting of a multimeter, the multimeter will definitely burn out. You can use the above mentioned method to connect a resistor to measure the current. You can also use a simpler method to connect a light bulb to determine whether the circuit is connected. Opinion
It is very dangerous to measure while the power is on. Try not to use it. What will happen if the power is turned off for a while?
It is possible to use the on-off switch to measure, and the multimeter will not be burned out. But you can't use resistor! ! ! !
It is not possible to measure continuity (actually on-circuit resistance) when there is voltage, otherwise the meter will definitely be damaged. Under normal circumstances (when there is power), the judgment is made by measuring the voltage at both ends (head and tail) of the line. The voltages are equal under path conditions. Other measures are more complicated and not very safe.
Connecting resistors and bulbs to the positive and negative ends of the electrical stage is less feasible in the field: For example, if the voltage is 220V and the power is not allowed to be cut off in the live state, when resistors or light bulbs are connected in series, the power must be cut off, which can easily cause electric shock. Let me put the problem simply. For example, the 220V L-phase at home and the 220V L-phase at work are both 220V to ground. Can we judge that they have figured it out? Similarly, there are two 220V voltage points in the cabinet. How to determine whether they are the same? It is of course not feasible to measure the voltage to ground separately.
If there are two power supplies, it won’t work with a multimeter. You can use an electric pen. If there is power or no power, you will know if you poke it. But don’t poke high voltage. Haha. This post was last edited by faner on 2009-3-9 17:13 ]
I think what the original poster means is to determine whether the AC power supply in two places comes from the same phase of the same transformer. Otherwise, neither of the above two will be connected. Therefore, when it is confirmed that the same transformer is supplying power, it is enough to determine whether the two are in the same phase. The way is to measure the line voltage. If it is 0, it means it is in phase: lol
Measure the voltage to ground at two points respectively. Are they both 220V? Are you sure? If this is the case, I think you can use the on-off setting of a multimeter to measure continuity. reason: The voltage to ground at both points is 220V, which means there is no voltage between the two points, and there is no current. The multimeter will not be burned out, but be careful not to cause an electric shock accident.
It's a bit dangerous, but you can measure continuity. Try not to measure like this.
I have a solution that works: Directly measure the voltage between two points. If there is voltage, there must be no connection. If there is no voltage, use a resistor or on-off switch to test continuity.
You can use voltage to measure continuity. When there is voltage, it indicates an open circuit. When there is no voltage, it indicates a path.
This question seems simple, but actually it is complicated when you think about it. The problem is that the actual situation changes a lot! I think: 1. It is not advisable to use a multimeter for live measurement. If a loop is formed with the load, neutral line or ground line, the meter will definitely be damaged. ； 2. There is a problem when measuring the neutral line or ground line. If this line is open circuit and the voltages at both ends are in different phases, the measurement will not be accurate. ； 3. There is also a problem when measuring line voltage on a pair of phase lines. If the two ends of the line are in different transformers, or the ABC phase sequence is incorrect, this may not be accurate. To sum up, I feel that this last solution is more feasible. You can use a tool similar to a clamp meter to measure small currents. If the current values at the two places are consistent, you can judge that they are connected. The premise is that they must form a loop with the load. If they are not consistent, it is an open circuit. At least it is not a phase sequence line. But this kind of instrument seems to be only available in Fluke.