Dc or Ac?

Most recent answer: 10/22/2007

Q:
How can I know whether one device use AC or DC sources phisically??
- Iyung (age 20)
Indonesia
A:
There is no ’sure fire’ way of knowing.  There are some clues, however.   If you measure the resistance of the input plug with an ohmmeter and find a small value, a few tens of Ohms at most, then it is likely there is an input transformer that requires an AC  source.

Lee H

Of course it’s important then to know what voltage and frequency it’s designed for. If it’s designed for 120 V (or even worse, for 24 V), it would probably be destroyed if you applied 220V.  Mike W.

(published on 10/22/2007)