How does the multimeter test whether the circuit is connected or not? The multimeter measures whether the circuit is connected or not
One of the simplest functions of the multimeter, you can switch the gear of the multimeter to the ohm symbol (Ω). Remember the value obtained by connecting the two measuring pens together, and then use one of the measuring pens to connect one end of the line to be measured and the other to the other end. If the value you remember does not work, there will be no response or value. big.
First of all, make sure that the circuit under test has no power, then put the multimeter in the ohm position, and first short the two test leads of the multimeter to see if it returns to zero. If you don't come back, you should write down the value at this time, and then use a multimeter to measure the circuit. If the resistance value of the tested circuit is the same as that of the experiment just now, then the point circuit is turned on.
The easiest way is to use a multimeter to test whether the L and N wires of the power plug have resistance. Normally, there is resistance. Preliminary rule out the power line, and whether there is a fuse inside, if you use a multimeter to measure whether it is open (if you are not familiar with electricity, do not operate it with electricity).
How to use a multimeter to detect the leakage fault of the lighting circuit
Once leakage occurs in the lighting circuit, it will not only waste electric energy, but also may cause electric shock accidents. The essence of leakage and short circuit is the same, but the degree of accident development is different. Severe leakage may cause short circuit. Therefore, the leakage of lighting lines must not be taken lightly. The insulation of the line should be checked frequently, especially when leakage is found, the cause should be found out in time, the fault point should be found, and it should be eliminated.
The main reasons for the leakage of lighting lines are: first, the insulation of wires or electrical equipment is damaged by external force; second, the long-term operation of the line leads to aging and deterioration of the insulation;
First, determine whether there is indeed a leakage. Use the R×10k range of the pointer multimeter to measure the insulation resistance, or place the digital multimeter in the AC current range (equivalent to an ammeter at this time), connect it in series to the main switch, turn on all the switches, and remove all loads (including Light bulb). If there is current, it means that there is leakage. After confirming the leakage of the line, you can continue to check according to the following steps.
1. Determine whether it is the leakage between the phase line and the neutral line, or the leakage between the phase line and the earth, or both. The method is to cut off the neutral line. If the ammeter indication remains unchanged, it is the leakage between the phase line and the earth; if the ammeter indication is zero, it is the leakage between the phase line and the neutral line; Leakage between line, phase line and earth.
2. Determine the leakage range. Take off the shunt fuse or pull open the circuit breaker. If the ammeter indication remains unchanged, it means the bus leakage; if the ammeter indication is zero, it is the shunt leakage; All have leakage.
3. Find the leakage point. After the above inspection, turn off the switch of the line lamp in turn. When a switch is turned off, the ammeter indicator returns to zero, and the branch line is leaking; if it becomes smaller, it means that there is leakage in other places besides the branch line; If the ammeter indication remains unchanged after all the lamp switches are turned off, it means that this section of the main line is leaking. By narrowing down the scope of the accident in turn, you can further check whether there is leakage at the joints of the line and where the wires pass through the wall. After finding the leakage point, the leakage fault should be eliminated in time. The load end starts to detect step by step towards the front end, and it can be judged by checking whether the work is caused by the line or the component. After eliminating the short-circuit fault point, install a qualified fuse and then send power.
