David Karol

Staff member
Jan 10, 2011
San Francisco, CA
We’ve had a few posts recently about blown up gear due to power problems. Here is a basic metering procedure that should give you a good indication of the safety of a standard North American receptacle (NEMA 5-15R or 5-20R).
Standard disclaimers: 

Performing this test can give you reasonable assurance that a receptacle is properly wired and functioning, however it does not guarantee that the receptacle is good – there are still possible fault conditions that may not be revealed with this test.
Performing this test requires sticking conductive things – multi-meter probes – into an unknown electrical supply. This has the potential to create an electric shock hazard if you touch the metal tips of your meter probes (duh), and if things are really wrong, you may cause your multi-meter (especially if it’s a cheap one) to explode.

Proceed at your own risk (though testing is a lot less risky than plugging gear into an unknown receptacle).
Anatomy of a Receptacle
An electrical...

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