transformer voltages read too high

Thread Starter


Joined Feb 22, 2011
My volt meter, ($25 Vellemann) persistently shows output DC voltages from transformers as TOO HIGH as compared with the nominal output voltage posted on the side of the various transformers. I have a whole box of 5, 9, 12, 14v transformers and they all show the same 50% (approx.) too high reading then expected. A 5v output shows 8v. A 12v might show 18v, etc. I use the transformers successfully on appliances and nothing blows up, so I'm assuming it's the voltmeter that's at fault. But when I use the same voltmeter on D, C, AA, AAA batteries the meter shows the expected voltages. Also I have a voltage regulator "chip" that outputs 5v and the volt meter shows 5 volts DC output exactly. So the misreading seems specific to transformers. Can anyone explain this? By the way, there are fresh batteries in the voltmeter.


Joined Apr 24, 2011
The voltage marked on a transformer is the voltage at the rated load, and in my experience it is still on the generous side.

So it should read high. Very high at no load (as it is for the measurement as you are taking it).