What is the practical use of a multimeter for measuring resistance
1. Coil type: 1. Two probes, measuring both ends of the coil, used to determine whether the coil is disconnected. The conducting buzzer will sound, but if it is not conducting, the buzzer will not sound.
Measure the resistance of the coil to ground and determine if the insulation layer of the coil is burnt out, with one probe at one end of the coil and the other probe at the ground wire.
3 contact types, such as the main contact and secondary contact of contactors and intermediate relays. Place the probes at both ends and measure whether the contact is good to determine whether the contactor should be replaced.
4 diodes/transistors. By measuring its resistance value, the diode has unidirectional conductivity, which can determine the positive and negative poles of the diode, as well as the quality of the diode and whether it has been reverse breakdown.
The resistance range of a multimeter also serves to measure the conduction voltage of the diode. Select the resistance gear 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 determine whether the quality of the diode is good or bad.
When using a multimeter to measure resistance, the machine must not be electrified. Only when the power is cut off can the resistance be measured.
The above is only the usage and function of the multimeter resistance range.
The voltage range is also commonly used.
Using the voltage range of a multimeter, place one probe at the desired measurement point and the other probe at the reference point, usually a ground wire or metal casing, to measure whether the voltage meets the requirements of our design. The voltage between the live wire and the ground wire is 220V, and the voltage between the live wire and the zero wire is also 220V. The voltage between the live wire is 380V. Meeting these three numbers indicates that the incoming line is normal.
The Ohm range of a multimeter is the most commonly used range
When we repair or inspect circuits and components, we usually use Ohm gear. To summarize, the following functions or purposes are commonly used:
1. Measure the continuity of the circuit, such as the measurement of the motor coil. In many cases, a buzzer gear is also used for measurement
2. Measure the resistance values of each circuit and component to calculate its power and other parameters. For example, our electric furnace can calculate its heating power based on the measured resistance.
3. Used to judge the quality of a component, such as a chip or component. If the normal resistance value between two pins is 100 ohms, but it is actually 1K, or infinity, it must be that the component is broken. For example, a thermistor, if the resistance values at both ends are measured and do not change with temperature, then the thermistor should be broken
4. Measure the actual resistance value of the resistance in the circuit. Some color ring resistors cannot be seen clearly, and there is also a verification of the actual resistance value of the color ring resistor!
