How to use a multimeter to measure the voltage of AC contactor A1 and A2 in the power-on state
Use a multimeter with an AC voltage of 500 volts to connect directly to A1 and A2
Select the 750V gear of the multimeter AC voltage, look at the position of the jack, put the black and black test leads into the com. red test lead into the V jack, put the red and black test leads at both ends of A1A2, and measure the voltage value
Turn the multimeter to the highest gear and lower it according to the display! If the pointer type must be done, the pointer should be in the middle position, such as a digital electronic watch, the purpose is to reduce the measurement error, and also to reduce the proper gear!
Use a multimeter to measure the AC voltage file, 250v file (when the estimated voltage is 220v) or 500v file (when the estimated voltage is 380v). Connect the two test leads to A1A2 to see the reading.
It is so simple that you can talk about the problem without thinking, first use the Ac high-level measurement to see if the result value is not good or wrong, and then use the Dc high-level measurement
Directly use a multimeter to set the 600V voltage range, and use the test pen to test it. There is no positive and negative poles in the AC power supply, and the test pen measures A1 and A2. It is clear at a glance whether there is power or not.
First determine the known voltage of the terminal to be tested. Most of the factory electricity is ≤380V AC, and the civilian use is 220V AC. Set the multimeter to AC 500V and measure it directly!
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?
Use a multimeter to measure the resistance at both ends of the electrical plug in your home is indeed different.
If you are measuring a kettle or an electric kettle, or a table lamp that uses 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 pointers will change when using a multimeter for transformer step-down rectification, and some use switching circuits 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.
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