The method of distinguishing between AC and DC using a multimeter
How to quickly distinguish whether a power supply is DC or AC using a multimeter? Generally, people can make a rough judgment based on intuition. For example, batteries are usually DC, while the power on the socket at home is usually AC. However, if there is a power supply plugged into a socket at home, and the power label falls off, then it is necessary to consider how to distinguish whether the power supply is AC or DC.
It is easy to distinguish using an electric pen. If this article simply states that using an electric pen to distinguish itself is not very meaningful, it is better to share a somewhat technical example of using a multimeter to distinguish whether the power supply is DC or AC.
For AC power, there is no distinction between positive and negative poles. When measuring with a multimeter in the AC range, the results are actually the same for both positive and negative measurements. However, when measuring DC power with a multimeter in the DC voltage range, this is not the case. There is a difference of "-" between the positive and negative sides, which can also distinguish between AC and DC. However, there is still a problem. To measure this result with a multimeter, it is necessary to know whether the power supply is DC or AC, otherwise selecting the wrong range will not display the result.
So, we need to come up with another method. Assuming that the power source to be distinguished is AC, we choose a larger range AC gear for the multimeter, bend the black probe about three times, and hang the black probe in the air. It is best not to touch the head of the black probe with your hands. For AC voltage range, touching the black probe is not dangerous, but if you accidentally touch the black probe and the red probe is inserted into the socket, it is very dangerous. Therefore, for safety reasons, it is best not to touch the black probe with your hands.
The next step is to insert the black probe into any socket of the power supply. If it is AC power, you will find that the number can be displayed when one of the two electrodes of the power supply is inserted into the socket. If this situation occurs, it indicates that the power supply is AC power, otherwise it is DC power.
The following image is a real-life test of communication, and it can also be seen that there are no numbers appearing on the display screen of the multimeter.
How to quickly distinguish whether a power supply is AC or DC using a multimeter?
But when the watch pin is replaced and inserted into the power socket, the number can be displayed on the display screen. If the number can be displayed, it indicates that the power supply is AC power. For DC power supply, no matter how you insert it, there is actually no voltage when inserting a watch pin.
