Newsgroups: sci.electronics
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: How can I recognize true ground?
Message-ID: <1989Jul7.155721.19105@utzoo.uucp>
Organization: U of Toronto Zoology
References: <18425@mimsy.UUCP>
Date: Fri, 7 Jul 89 15:57:21 GMT

In article <18425@mimsy.UUCP> spector@brillig.umd.edu.UUCP () writes:
>Question from a novice: My house has "two prong" outlets.  I've been told
>that the center screw and casing of the outlet boxes is generally grounded,
>so that I will have a correctly grounded outlet if I attach the wire of a
>"3 to 2 adapter" to the center screw.  How do I (a vertual electronics
>know-nothing) check to see if this is working in my case?

If you are really, seriously concerned about whether it really is grounded,
you can't assume that the screw is grounded, and in fact you can't assume
that the third prong in a three-prong outlet is grounded -- electricians
do get sloppy now and then.

I'm unable to think of a quick no-equipment test to make sure; perhaps one
of the higher gurus can.

>(I am doing this to comply with my computer's manual's warning not to defeat
>the ground plug.  Is this really a serious problem? ...

Long odds that warning was written by lawyers worried about liability
rather than by technical people.  Grounded outlets *are* a good idea,
though, and I'd proceed cautiously.  Certainly tying the wire to the center
screw is worth doing.
-- 
$10 million equals 18 PM       |     Henry Spencer at U of Toronto Zoology
(Pentagon-Minutes). -Tom Neff  | uunet!attcan!utzoo!henry henry@zoo.toronto.edu