How do I test an extention cord with volt meter?

Answer 1

Set the voltmeter to the "AC" setting (to measure alternating current), plug the extension cord into a known working outlet, then stick one probe in one of the receptacles in the plug of the extension cord and plug the other probe in the other receptacle.

With a regular voltmeter, you won't be able to test whether or not the extension cord is good unless you plug the cord into a known good power source.

Answer 2

I would not recommend testing with a voltmeter for two reasons:
1) the danger of getting an electric shock.
2) using almost any voltmeter will not reveal problems such as many broken strands in the conductors at either end. They are high-impedance devices that would still register full line voltage even through fairly high impedance.

Do a visual inspection. If any insulation is cracking at either end, throw it away. If you see any damage caused by heat at either end, throw it away. Many extensions are 16 or 18 gauge wire and cannot handle the 15 or 20 amps that the house lines/outlets can. If they have been used to carry excessive loads, you will likely see some heat damage (in which case, throw it away). You can use an ohmmeter to verify the conductors are still connected (assuming the visual inspections checked good). In this case, stick one probe into the female end and check the male end for continuity (both conductors). Of course, the extension cord would be disconnected from the mains whilst performing this test.

You can test an outlet by plugging in a known good lamp or vacuum cleaner (almost anything - just make sure it runs before plugging into the unknown outlet).

Plugging voltmeter probes into outlets isn't a particularly good idea unless you know what you are doing. They do make neon test lamps with three prong connectors to plug into outlets/extension chords which not only indicate power, but indicate proper polarity and grounding - a *much* better solution and they are not horribly expensive.

The narrow slot should be "hot" and test 110 volts to the wide slot (neutral) and also test 110 volts to ground (the round hole). You don't want the wide slot testing 110 volts to ground - if so, you've got a serious problem.

Good luck!


Best regards,
Jim

Answer 3

for telephone or for 110 V electric ?

you can test it with a volt meter, but i would use an ohmmeter instead, both features are usually available on multimeters.
set it to resistance.

-1- for phone
you need to test the two center wires of the male and female connector. they are used for line 1. if you use multiple lines on the same plug, the line two will the the two outer wires.
see detailed test procedure below.

-2- for house electricity
get both extension ends on a table and put one probe of the ohm-meter in the wide hole on one side and the other probe on the thick balde on the other. you should get a reading close to 0 ohms.
Now do the same one the other side (narrow hole and blade) and you should also get a reading close to 0.
if both tests fail, maybe the plugs are swapped on one side, so you could try thick to narrow. for most use it will be fine but it will prove that this extension is a little funny and i would not trust it.

Finally make sure that between the two holes you get a reading of infinity (that would be the same as measuring the reading between the two blades)

if all three test are successful, your extention cord in working fine.

You could do it with a voltmeter and check that you get 110 V AC but you would not know whether the ends are connected the right weay around, and if you can do it safely without pluggin it, why would you want to do it the dangerous way ?



stay safe.

-Francois