What is the reason for using a multimeter to test the ohm range of the household appliance plugs, some are connected and some are not?
If you are measuring electrical appliances such as kettles or electric kettles, or desk lamps that use the original incandescent lamp, when the switch is turned on, the resistance at both ends of the measuring plug should be about 100 ohms. When measuring the two ends of the plugs of TVs, refrigerators, washing machines, etc., the resistance values are different, because the plugs of each electrical appliance are different from their internal power circuits, and display different resistance values.
After personally experiencing the washing machine when the switch is turned on, the resistance measured at both ends of the plug is about 200 ohms for the motor in the washing machine.
Some household appliances such as LCD TVs and refrigerators have a resistance value close to infinity under normal use.
Based on the above, using a multimeter to measure the on-off of the electrical plug to judge whether the electrical appliance is good or bad is not suitable for all electrical appliances, and the multimeter is not a panacea. Only suitable for some electrical appliances, such as electric kettles, kettles, rice cookers, electric soldering irons, motor coils, incandescent light bulbs, etc.
Before measuring household appliances, you must understand the circuit diagram of the appliance, especially the power input circuit. Some use a transformer to step down and rectify the pointer will change when measuring with a multimeter, and some use a switch circuit or other circuits, and the pointer may not necessarily change. In addition, the circuit breaker multimeter will have no indication. Therefore, before measuring, compare the drawings or open the electrical appliances to check the circuit structure, so as to avoid misjudgment.
The power supply methods of various household appliances are different, and the power is also different, so the measured resistance value is also different. If it is a switching power supply, it has a diode protection start inside, so the resistance cannot be measured.
