How to use a multimeter to check for short circuit, open circuit and leakage?

In our family, there are often some small faults in the use of electricity. Many friends want to know how to solve these glitches. In fact, I personally suggest that it is best to find a professional electrician to check after the home electricity failure, and try not to mess around yourself.

However, it is also necessary to learn some knowledge about checking for faults in the relevant aspects of the circuit. For example, how do we use itMultimeterWhat about short circuits, open circuits and leakage?

Using a multimeter to measure whether there is a short circuit in a circuit is actually very simple. But there is a premise, everyone must pay attention to the operation of power-off. Otherwise, not only is it dangerous, but your multimeter may burn out.

After disconnecting the power supply, we find the wires to be tested for the loop. It's best to be able to expose the letter inside. Now it's time to get ready to measure, turn on the multimeter, and zero it.

At this time, we need to choose the gear of the multimeter in the buzzer gear, that is, the light-emitting diode.

That gear. Then insert the black watch pin into the common end, and the red watch hand into the voltage resistor jack. We measure whether there is a short circuit between the two wires by touching the hand of the black pen and then touching the hand of the red pen to the other wire.

If the multimeter light flashes or beeps at this time, then there is a short circuit between the two wires. Using the same method, we can test whether there is a short circuit between several other wires. At the same time, it can also be measured whether there is a short circuit between the wire and the ground.

When the ground is short-circuited, the black pen is grounded, and the needle of the red pen touches the core of the wire, so that one by one is measured. The result shown is the same as above, and the beep indicates a short circuit.

The so-called circuit opening of the circuit is that the wires in the circuit are disconnected somewhere in the middle and do not pass. Then use a multimeter to measure the open circuit of the line, and we also use a buzzer. In this case, it is necessary to use one multimeter pen with the needle touching one end of the wire, and the other multimeter pen with the needle touching the other end of the wire.

At this time, some friends may ask, the pen of the multimeter is not so long, in fact, we can use the wire to extend the method to achieve. To measure the open circuit of the circuit, we also first disconnect the power supply, then find the wire we want to measure the circuit, find the two ends of the wire, and then expose the core inside. The measurement is also to use the buzzer of the multimeter, the range of the multimeter is hit on the buzzer, and then the black pen is inserted at the common end, and the red pen is inserted into the voltage resistance hole, so that the measurement can begin.

If the multimeter beeps at this time, it means that the wire is a path and there is no open circuit, if the multimeter does not have any display, then the wire is open, that is, it is disconnected somewhere in the middle.

Short circuit: When measuring short circuit faults, always make sure to disconnect the power supply and remember not to operate with electricity. Short-circuit measurement uses the buzzer or ohm file of the multimeter to measure, when the measurement is more intuitive, when the line is short-circuited, the multimeter will directly "beep", the principle of the buzzer file is when the measurement resistance is less than about 75, the multimeter beeps, if you want to know more accurately the resistance between the two lines, you can use 200 measures to measure.

Using the buzzer file measurement, sometimes the actual internal resistance between the two signals is small, it is easy to misjudge, such as the relay contactor coil, many relay contactor coil impedance is less than 75, the use of the buzzer file measurement will beep to think that it is a short circuit, in fact, there is not.

Open circuit: Use the multimeter buzzer to measure both ends of the line, if the line is intact, the multimeter will beep, if the multimeter does not beep, it indicates that the line between the two meter pens is broken. Note: The power supply must be cut off for open circuit measurement, and it cannot be operated with electricity.

Leakage: Leakage measurement is mainly to detect whether the live wire, neutral wire and wall are well insulated, and whether the power cord (live wire, neutral wire) is well insulated from the metal shell of electrical appliances, such as refrigerators, induction cookers, microwave ovens, electric teapots and other metal shells.

Short-circuit measurement is very commonly used in electrical maintenance and component fault location, and when measuring short-circuit faults, make sure to disconnect the power supply and remember not to operate with electricity. Short-circuit measurement is measured using the buzzer or ohm file of the multimeter, when the measurement is more intuitive when using the buzzer, the multimeter will directly "beep" when the line is short-circuited

Connect the meter to both ends of the circuit. A zero current is an open circuit. The current is too large and unstable, and a resistance value of zero is a short circuit. Leakage is the generation of electric current on the outer sheath of the wire.

How to check for short circuits, open circuits and leakage with a multimeter? The master electrician will teach you step by step.

If two lines intersect, if there is no signal, then there is a problem.

Summary. There are three easiest ways to check leakage with a multimeter: 1. Power-off measurement:

First of all, turn off all electrical appliances in the home, adjust the multimeter to RX10K gear, one pen is connected to the live wire, and the other meter pen is grounded, the resistance should be shown infinity, otherwise the electricity will leak. 2. Live measurement: First of all, the multimeter is adjusted to 250 volts AC voltage level, and then the leakage electrical shell is measured, one pen is connected to the shell, and the other meter is grounded, if the pointer shows that the voltage is between 30 and 50 volts, change to AC 50 volt gear.

If the power supply is confirmed to be more than 30 volts, it is considered leakage, and less than 30 volts is normal. 3. Leakage measurement between the live wire and the neutral wire (or two live wires): turn off and disconnect all electrical appliances in the home, and then measure the resistance between the live wire and the neutral wire, which should be infinite, otherwise it is a leakage phenomenon.

There are three easiest ways to check leakage with a multimeter: 1. Power-off measurement: First of all, turn off all electrical appliances in the home, adjust the multimeter to the RX10K file, one pen is connected to the live wire, and the other meter pen is grounded, the resistance should be shown infinity, otherwise the leakage.

2. Live measurement: First of all, the multimeter is adjusted to 250 volts AC voltage level, and then the leakage electrical shell is measured, one pen is connected to the shell, and the other meter is grounded, if the pointer shows that the voltage is between 30 and 50 volts, change to AC 50 volt gear. If the power supply is confirmed to be more than 30 volts, it is considered leakage, and less than 30 volts is normal.

3. Leakage measurement between the live wire and the neutral wire (or two live wires): turn off and disconnect all electrical appliances in the home, and then measure the resistance between the live wire and the neutral wire, which should be infinite, otherwise it is a leakage phenomenon.

2.When using a universal meter, do not touch the metal part of the watch with your hands, on the one hand, to ensure the accuracy of the measurement, and on the other hand, for your own safety. 3.

When measuring a charge, never shift gears during the measurement. 4.During the use of the universal meter, it must be placed horizontally, otherwise it will cause errors.

5.After the universal meter is used up, the switch should be turned to the maximum level of alternating current, if it is not used for a long time, remember to remove the battery. 6.

If you notice that the meter is damaged, do not continue to use it. And before using the table, it is necessary to carefully check the housing, especially the insulation next to the terminals. 7.

Next, check whether the pen is damaged or on/off, and replace the damaged pen before use.

The method of measuring short circuit and open circuit of the universal meter is as follows:

First, in the case of a power failureMeasuring the European mother, the red and black meter pen measuring the fire wire, the ground wire, and the meter is low resistance, that is, a short circuit.

Second, in the case of power-onMeasuring voltage block, red and black meter pen measuring live wire, ground wire, and zero voltage of the meter, that is, open circuit.

3. In the case of power-onMeasuring voltage block, red and black meter pen measuring live wire, ground wire, electric meter has voltage, that is, grounding. If the meter has no voltage, it is not grounded.

Fourth, the path has: a certain resistance. There is a beeping sound. Short circuit: The resistance is zero. There is a beeping sound. Open circuit: Resistance infinity. No beep.

How to use the multimeter and precautions:

1) Before using the multimeter, "mechanical zeroing" should be carried out, that is, when there is no measured electricity, the multimeter pointer should be pointed at the position of zero voltage or zero current.

2) In the process of using the multimeter, do not touch the metal part of the meter pen with your hands, so that on the one hand, you can ensure the accuracy of the measurement, and on the other hand, you can also ensure personal safety.

3) When measuring a certain amount of electricity, it is not possible to shift gears at the same time as the measurement, especially when measuring high voltage or high current, more attention should be paid to it. Otherwise, the multimeter will be destroyed. If you need to change gears, you should disconnect the watch pen first, and then go to measure after changing gears.

4) When the multimeter is in use, it must be placed horizontally to avoid errors. At the same time, care should be taken to avoid the influence of external magnetic fields on the multimeter.

5) After the multimeter is used, the transfer switch should be placed in the maximum gear of AC voltage. If it is not used for a long time, the battery inside the multimeter should also be taken out to avoid the battery from corroding other devices in the meter.

Three-phase electric leakage and short circuit are divided into three steps: 1. Cut off the power first, detach the three-phase power from the main power supply, and let the load be completely unloaded. 2. The three wires are artificially A, B, C, and use the multimeter resistance file to measure the short-circuit problem first, that is, AB, BC, AC at this time the measurement result resistance is infinite, and the test results between the three wires The multimeter pointer does not swing as a positive warning, if the resistance is found to be particularly small, it means that the line is short-circuited and the wheel bridge.

3. Note that in the case of three-phase electricity detachment from the total power supply, use the multimeter rod at one end on the power supply, and the other end take turns to take the ABC three wires to see if there is voltage, in the case of no load should be no voltage or resistance is infinity, if the measured results have voltage and resistance, it means that the line is leaking, and it is normal for Layou to be the opposite.

First of all, you need to be able to use a multimeter. 1.Find out the ins and outs of the line to be inspected, and disconnect the open-air switch of the power supply to ensure personal safety.

2.Check the power. Use the AC voltage of the multimeter to 700V and check whether the lower end of the output is disconnected.

3.Disconnect the load (e.g., fluorescent lamp) of the circuit under test and pull the multimeter to the buzzer setting. The resistance of the two working wires should tend to infinity.

If the circuit is short-circuited, the multimeter will make a sound. 4.If there is a PE grounding wire, pay attention to check it.

At this time, there can be no buzzer between the working neutral line and the PE. A short circuit is when the phase wire and the phase wire, the phase wire and the neutral wire are directly connected without any load. In general, grounding refers to a short circuit between the phase wire and the ground wire.

Voltage, what is voltage? The potential difference between two points is the voltage. Before measuring, cut off the power supply and load, that is, pull down the switch, unplug the electrical appliances, and directly measure the resistance between the phase wire, and between the phase wire and the neutral or ground wire with resistance break.

Normally, it is infinity and the meter will show 1. As for the relationship between the zero line and the ground wire, it is not clear in a few words, that is, the difference between the three-phase four-wire system and the three-phase five-wire system. To check whether the line is short-circuited or grounded, you can judge what kind of power supply system it is.

The approach is slightly different. For short circuits or grounding, you have to unplug the power supply to disconnect the load, and some leakage switches have straight neutral wires. You have to remove the zero wire to measure it, because the zero line and the ground wire are separated by one line.

Digital multimeters use the diode position, and analog multimeters use the R1 position. These pens are connected to the live wire, the neutral wire, and the ground wire. The small resistance value of the fire neutral line is a short circuit, the small resistance value of the fire grounding wire is grounding, and the small resistance value of the zero ground wire is the zero line grounding.

If the diode gear and R1 gear cannot be measured, use 2m ohm gear and 10m ohm gear to measure. If the line is slightly longer, it is recommended to measure it with a shake meter. When distinguishing between circuit leakage and grounding, select the range of the multimeter.

In general, when measuring line leakage, use the 10k gear of the multimeter. When the line resistance is greater than or equal to meohm, the line grounding condition is good; Otherwise, the line leakage and leakage protection actions indicate the leakage status. If a megohmmeter is used, shake the megohmmeter at a constant speed to reach 120 revolutions, and the line leakage value will be when the reading is stable.

When measuring short circuits, select the multimeter x1 gear. If the multimeter shows 0 or the resistance value is small, it means that there is a short circuit in the line. In the event of a power outage, make sure the line is unpowered and that all loads on the line to be inspected have been cut off (or disconnected).

Then, test the resistance values of the phase and neutral wires with a multimeter resistance (preferably less than 100 ohms), and then measure the resistance values of the phase and ground wires. By comparing the two values, it can be concluded that the small resistance value is a phase-to-ground short-circuit or a phase-to-zero short-circuit. If there is a 10% difference in the resistance value between the neutral wire and the motor phase under test, the resistance value is too small and there is an inter-turn short circuit.

The windings need to be removed and new ones embedded. For 380V motors, the resistance value measured between the neutral and the phase and the housing is greater than 500k to 2m, if it is less than half a m to 1, the winding needs to be dried before use. If it's close to 0m, you'll need to embed a new winding!

With the resistance gear, 0 resistance is a short circuit, and infinity is an open circuit.

Short circuit, the resistance is almost 0. Open circuit: Resistance infinity.

To check if there is a short circuit in the circuit using a multimeter, you can follow these steps:

Select the knob of the multimeter to the resistance level ( ).

Turn off the power in the circuit and disconnect all connections in the circuit.

Connect the two probes of the multimeter to each of the two points in the circuit that need to be checked.

If there is a short circuit in the circuit, the multimeter reading will be very small, or even zero. If there is no short circuit in the circuit, the multimeter will read very large, or show infinity ( ).

If the multimeter reads very small or zero, there is a short circuit in the circuit. At this point, it is necessary to check the components and connections in the circuit for problems, and find and fix the short circuit problem.

If the reading of the multimeter is very large or infinity ( ), there is no short circuit in the circuit.

It should be noted that when checking for a short circuit in the circuit, it is important to make sure that the power supply is turned off and all connections have been disconnected. In addition, if there is high voltage or high current in the circuit, it should be detected with professional test instruments to ensure safety.

When there is a short circuit in a circuit, the current flows along the short circuit path, causing the voltage in the circuit to drop, overheating or even damage to the circuit components. Therefore, it is very important to detect and repair short circuit problems in time.

In addition to using a multimeter to check for short circuits in the circuit, you can also check using the following methods:

Visual inspection: Check the components and connections in the circuit for obvious damage or short circuits, such as scorching, expansion, deformation, carryover, etc.

Sniff inspection: Sometimes the components or connections in the circuit will be overheated and cause a burnt or burnt smell, and the smell can be used to determine whether there is a short circuit.

Touch inspection: Sometimes the components or connections in the circuit can become very hot due to overheating, and you can tell if there is a short circuit problem by touch.

Thermography: Infrared thermal imagers can be used to detect the temperature distribution in a circuit and thus determine if there is a short circuit.

In short, it is very important to find and repair the short circuit problem in the circuit in time to avoid damage to circuit components and safety accidents.