How to use a multimeter to determine whether an AC or DC voltage is present
How to use a multimeter to quickly distinguish whether the power supply is DC or AC? Generally speaking, everyone can judge roughly by intuition. For example, batteries are generally DC power, and the power in the sockets at home is generally AC power, but if there is a plugged in socket at home If the power supply label has fallen off, you have to consider how to identify whether the power supply is an AC power supply or a DC power supply.
It can be easily identified with an electric pen. If this article directly talks about using an electric pen to identify it, it doesn't make much sense. Let's share a somewhat technical method of using a multimeter to identify whether the power supply is DC or AC.
For alternating current, there is no distinction between positive and negative poles. When measuring with a multimeter in the AC setting, the results are actually the same when measured forward and backward. However, when direct current is measured with a multimeter in the DC voltage setting, this is not the case. There will be a "-" sign difference between the two sides. From this point, AC or DC can also be distinguished. However, there is still a problem. If you want to use a multimeter to measure this result, you actually still need to know whether the power supply is DC or AC in order to do this. Otherwise, if you select the wrong gear, the result will not be displayed.
So we need to come up with another method. Assume that the power supply we want to identify is AC. Select an AC range with a larger range of the multimeter, bend the black test lead, make about three turns, and leave the black test lead in the air. , it is best not to touch the black test lead with your hands. For the AC voltage setting, there is no danger in touching the black test lead. However, if the AC setting is selected by mistake, if you accidentally touch the black test lead, and the red test lead It is plugged into the socket, which is very dangerous at this time, so for safety reasons it is best not to touch the test leads with your hands.
The next step is to insert the black test lead into any socket of the power supply. If it is AC, you will find that the number can be displayed after one of the two electrodes of the power supply is inserted into the socket. If this happens, Indicate that this power supply is AC power, otherwise this power supply is DC power.
The picture below is a live picture during the test communication. From the picture, you can also see that there are no numbers on the multimeter's display screen.
How to use a multimeter to quickly distinguish whether the power supply is AC or DC?
But when you change the position of the watch needle and insert it into the power jack, the number will be displayed on the display. If the number can be displayed, it means that the power supply is an AC power supply. No matter how you plug in the DC power supply, as long as you insert a watch needle, it will actually There will be no voltage.
