Originally Posted by EssexBoyRacer
Alternatively, the output voltage from an AC adaptor will tell you as well.
That's what I have infront of me, and it says 5V
To use the voltmeter set it to volts, up to a maximum that is above 14V and plug the leads in. If you have sockets to choose from, use the black one - might be labelled 0V, -ve, com etc. and the other one into something that says V, NOT A
To check you have it right, put it onto the battery and hope you see 12V ish.