How a Multimeter Measures AC and DC Voltage

　　If the AC/DC voltage range of the multimeter and the AC/DC type of the voltage being measured are correct, when measuring DC voltage, the digital multimeter will display a - sign and the pointer of the multimeter will swing in the positive direction.

　　When a digital multimeter uses the DC voltage range to measure AC voltage, the reading will be very small or almost zero. When a pointer multimeter uses the DC voltage range to measure AC voltage, the swing will also be very small or even nonexistent. The same is true when a multimeter uses the AC voltage range to measure DC voltage. At this point, you should realize that the voltage type being measured is incorrect, and you should reselect the correct AC and DC voltage type range of the multimeter.

　　In addition, when the voltage of the power supply to be measured is unclear, you should gradually switch to the high voltage gear and then the low voltage gear to ensure safety.

　　You can first measure with an AC voltage of 750V and look at the displayed value. If it is very small or basically not displayed, you can use the DC voltage range to test!

　　First use the maximum AC voltage for measurement, and after determining the range, use the appropriate range for accurate measurement. If no stable value is displayed, it is DC. Switch to the highest DC voltage to measure the approximate value. After determining the range, switch to the appropriate range for accurate reading.

　　Use the maximum AC voltage range to measure once in both directions. If the two voltages are the same, it is AC. Otherwise, it is DC.

　　Alternating current has no positive or negative poles; direct current has positive and negative poles.

　　This is a common sense for using a multimeter correctly. When you want to measure the voltage of an unknown power supply, you should set the multimeter to the maximum AC voltage level, and then adjust the level to the appropriate level based on the approximate measurement results to make accurate measurements.

　　It is very simple. Use a mechanical multimeter and measure from the highest gear down. Use the AC gear and DC gear respectively. If the AC gear cannot measure, the DC gear can measure it, which is direct current, and vice versa. In fact, you can judge whether it is AC or DC by the pins of the device structure.