Electrical Engineering

19. January 2022

How to test a power adapter with a multimeter

Do you want to check if a power adapter is still working correctly, or you are unsure which voltage is used? No worries, this can be tested easily if you have a multimeter.

Preparing the measurements

First, you should get your multimeter and power adapter ready. Attach the black probe to the COM port and the red one to the one with V=.

Turn on the multimeter and Switch to V= mode and choose between AC or DC depending on the output type of electrical current coming from the power adapter. Most common household power adapter output DC.

Did you know?

Common household sockets output AC current, in which the power supplies task is to convert it to the correct voltage and current (AC or DC).

Leave it on autorange or configure your multimeters range to display 2-digit voltages depending on the voltage of the power adapter.

Analogy of a power adapter plug

The outside of the power adapter plug is minus and the inside is plus.

So make sure to hold the black probe against the outside and the red one on the inside of the connector.

If it is showing a minus value, it means either the probes are reversed or the plug is wired wrong.

You should now be seeing the voltage the power adapter emits. It should be near the voltage written on the power adapter, with an acceptable tolerance of +-5%.

Voltage spikes beyond tolerance

If the voltage spikes up more than the tolerance, you probably have an unregulated power adapter. That means the output voltage is not regulated. Below you can find a page that gives some further explanation on the differences.

Click on the button to load the content from www.differencebetween.com.

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