What is the practical use of a multimeter for measuring resistance?
1. Coil type: Two probes, measuring the two ends of the coil, used to determine whether the coil is disconnected. The buzzer will sound when it is conductive, but it will not sound when it is non-conductive.
One probe is connected to one end of the coil, and the other probe is disconnected from the ground wire. Measure the resistance of the coil to ground and determine if the insulation layer of the coil is burned out.
2. Contact types, such as main contacts and auxiliary contacts of contactors and intermediate relays. Place the probe at both ends, measure whether the contact is good, and determine whether the contactor should be replaced.
3. Diode/transistor. Measuring its resistance, the diode has unidirectional conductivity, which can determine the positive and negative terminals of the diode, as well as its quality and whether it has been reverse broken down.
The resistance range of a multimeter also serves to measure the voltage at which a diode conducts. Select the resistance gear and switch it to measure the conduction voltage of the diode. The silicon transistor is 0.7V and the germanium transistor 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 charged. Only when the power is cut off can the resistance be measured.
Another commonly used option is voltage mode.
Using the voltage range of a multimeter, place one probe at the desired measurement location and the other probe at a reference point, usually a ground wire or metal casing, to measure whether the voltage meets our design requirements. The voltage between the live wire and the ground wire is 220V, and the voltage between the live wire and the neutral wire is also 220V. The voltage between live wires is 380V. Satisfying these three numbers indicates that the incoming line is normal.
The ohm range of a multimeter is the most frequently used range
When we repair or inspect circuits or components, we usually use the ohm range. To summarize, the commonly used functions or uses include the following:
1. Measure the continuity of the circuit, such as measuring the motor coil. In this case, many also use the buzzer mode for measurement
2. Measure the resistance values of various circuits and components to calculate their 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 components, for example, if a chip or component has a normal resistance of 100 ohms between two pins, but it is actually 1K or infinite, it must be a faulty component. Also, for example, a thermistor, measuring the resistance at both ends without changing with temperature, then this thermistor should be faulty
4. Measure the actual resistance value of the resistor in the circuit. Some color ring resistors cannot be seen clearly, and there are also verification of the actual resistance value of the color ring resistor!
