If you connect yourself to the uplugged computer via wrist strap, couldn't you be zapping the computer/chips with whatever static charge you had built up (eg, the surprising, sparking amount you get during the dry winter after walking on a carpet) on the way to the computer?
----- Original Message -----
From: Dean Kukral
To: [log in to unmask]
Sent: Friday, June 19, 2009 11:55 AM
Subject: [PCBUILD] It is neither necessary nor desirable to ground the case to a wall socket - follow-up
Although I have an MSEE, it is more in "computer engineering" rather than "power engineering." Even a degree in power engineering
does not qualify you to be an electrician, so I consulted two master electricians that worked for my REC, and paid one $60 to come
out and check my wiring.
Evidently, the way my house is wired was acceptable in 1977, but code has changed since then to add more grounding at the breaker
boxes. According to these electricians, my house is okay. I said, "Well, if I touch my saw or my refrigerator, that connects me to
neutral, doesn't it?" And they agreed that it did, but were not real concerned. They felt that the sockets were adequately
grounded. (Note, this applies to a house built in 1977 - not one built earlier!!) I am a little safer because I am not connected
to a city water main via copper pipe, so the floating neutral level in my house is at least consistent throughout the entire house.
Even if there is a positive voltage on something, it will be there on everything in the house.
So, I asked the question, "Is it safe to ground my computer to a wall outlet while I am working on it, using one of the cords that
has only one wire from the socket ground (actually neutral) to my computer?" The answer was, "Well if all the connections are
tight, it should be okay." Always an "if." And I said, "What if ...," and he agreed that there was some small chance of a problem,
but he seemed to think that it was very, very unlikely.
So there you have it. I am technically correct, but probably to a paranoid extreme. It is "probably okay" to ground your computer
to a wall socket "as long as all the wiring is okay." Remember, now, we are talking about a house built in 1977, so if you have an
older house your wiring might not be trustworthy. One of the references that Anna gave said that you should have a professional
check your house wiring first. (Well, who is going to do that just to upgrade a computer?)
I am going to remain paranoid and not work on my computer while it is plugged in to any part of a wall socket. After all, the
time-honored technique has been to use a wrist strap. I think that Laws of Physics support the contention that static electricity
will dissipate from a metal case quickly, but, even if it did not, at least the case and I will be at the same electric potential.
I am considering purchasing an anti-static mat. That would be the safest way to work on a computer. Should have purchased one
twenty years ago! The trouble is, where could I connect it to ground?? :) :)
Mr. Paranoid, a.k.a. Dean Kukral
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