how do you tell if the plug on a ac/dc adapter is positive on the inside and negative on the outside?

Question

What are all the different letters on the casing of the adapter mean, such as L.T.E. , some say CE, others have cOus with a UL in the circle?

Answer 1

The diagram on the adapter will show you the polarity. Look closely, though, because some of the diagrams aren't clearly drawn; I'd recommend a magnifying glass, just to make sure.

CE is the European version of UL, but for all of Europe, not just one country like UL. They have their own standards for electrical safety and interference. They are typically more stringent on insulation breakdown, since Europe typically uses 230V and electrocution can be a big problem, while UL is more concerned about fire prevention since 115V uses twice the current (twice the heat) as a 230V device.

Answer 2

Lte, and CE, sound like the electronics company that made it, and all companies, have to pass stringent rules to be allowed to be in the u.s. that's where the Underwriters Labratory UL, comes in they test everything to make sure it's safe to use, and not interferring with other electronics. and a plug that one is bare, and one is covered, Noone leaves a positive exposed to where you can ground it out! So that's negative...Or if you really want to check get out a voltohm meter, set it to ohms, touch the leads together, and ohm out the meter, by adjusting the knob to zero, then touch the bare lead, to one wire,of the meter, and case ground to the other and it should go back to zero again...meaning they are the same....The other way is to put it in voltage function 12 volts or whatever, then put both leads in the plug, if you have them right, pos. to pos. and neg. to neg. you get a reading, if reversed, the meter will try to go backwards....

Answer 3

Rule of thumb is that the inside contact is positive.
Look on the appliance and you will see a graphic usually a broken circle with either a + or - in the center, that is a mark of the polarity of the center hole or post.