What is the practical use of a multimeter to measure resistance
Multimeter to measure the effect of electric barrier.
1. Coils: 1. Two test leads, measuring both ends of the coil, the function is to judge whether the coil is disconnected. The buzzer will sound when it is on, but it will not sound when it is not.
2. One test lead is at one end of the coil, and the other test lead is broken at the ground wire, measure the resistance value of the coil to the ground, and judge whether the coil insulation layer is burnt out.
3. Contacts, such as main contacts and auxiliary contacts of contactors and intermediate relays. Put the test leads at both ends, measure whether the contact is good, and judge whether the contactor should be replaced.
4. Diode/transistor. Measure its resistance, the diode has unidirectional conductivity, you can judge the positive and negative poles of the diode, and you can also judge whether the diode is good or bad, and whether it is reversely broken down.
Another function of the multimeter's electrical barrier is to measure the conduction voltage of the diode. Select the gear to electric blocking, and switch it to measure the conduction voltage of the diode. The silicon tube is 0.7V, and the germanium tube is 0.3V. To judge whether the quality of the diode is good or bad.
Note that when measuring resistance with a multimeter, the machine must not be charged. Power off to measure resistance.
The above is just the usage and function of multimeter electric barrier.
The more commonly used is the voltage block.
Use the voltage block of the multimeter, put one test lead at the place you want to measure, and the other test lead at the reference point, usually the ground wire or the metal case, and measure whether the voltage meets the requirements of our design. There is 220V between the live wire and the ground wire, and 220V between the live wire and the neutral wire. The voltage between live wire and live wire is 380V. Satisfying these three numbers means that the incoming line is normal.
The ohm gear of the multimeter is the most used gear
When we are repairing or checking circuits and components, we usually use ohm files. To sum up, the commonly used functions or uses are as follows:
1. Measure the continuity of the circuit, such as the measurement of the motor coil. In this case, many of them also use the buzzer to measure
2. Measure the resistance of each circuit and component to calculate its power and other parameters. For example, our electric furnace can calculate its heating power according to the measured resistance.
3. It is used to judge whether the component is good or bad. For example, for a chip or component, the normal resistance between a certain two pins is 100 ohms, but the actual resistance is 1K, or infinite. It must be that the component is broken, such as a thermistor. Measure the resistance at both ends, if it does not change with temperature, then the thermistor should be broken
4. Measure the actual resistance value of the resistors in the circuit. Some color ring resistors cannot be seen clearly, and the actual resistance value of the color ring resistors is also verified!
Also note that:
1. Remember to zero the ohm before measuring the resistance of the ohm gear of the pointer multimeter, and then adjust the zero when changing the gear position. For the digital multimeter, you must pay attention to the wire resistance of the test lead, especially when the inferior test lead line group is very large (generally 0.2 about)
2. When measuring the resistance value of wu components on the circuit board, it is recommended to disconnect one foot for measurement, so that it will not be affected by the circuit and the measured data will be accurate
The electric blocking I use the multimeter is mainly in these four aspects: one is to use the lowest level of electric blocking to measure whether the circuit is on or off; Whether the motor is short-circuited to the ground, leakage, etc.; the third is to use the appropriate gear of the electric block to detect the quality of each component on the circuit board, such as the resistance of the three-stage tube, etc.; the fourth is to use the electric block of the pointer multimeter to detect some capacitors The parts are probably good or bad. I usually use a multimeter to block it like this.
Most electrical equipment has a standard resistance value. We use a multimeter to measure the resistance to help determine whether the electrical equipment is normal or abnormal. Of course, it does not mean that the abnormality of the two resistances measured by this meter is definitely abnormal. There are many factors affecting the resistance of the electronic equipment, such as density. . Mass, area. Temperature has an effect. For example, when you measure 20 degrees Celsius, the resistance is 100 ohms, and it may become about 90 at 40 degrees Celsius, so this is just an auxiliary test.
