DonC said:
OK, I'll be contrary
What you are doing is all OK --- but in my
experience overkill <DUCK!>
Unplugging the power cord and touching the case has been my standard
procedure since opening computer cases began. And I've never had a problem
caused by static discharge or electrical flow*. If you walk across carpet
or anything else that could cause a build up, touch the case. Kept yourself
at the case's voltage potential. It really easy. We used to have a geekie
nerd who used the wrist strap and every other precaution he could think of.
We irreverently joked that he should clip one end of a wire to case and the
other end to his testicles. Sorry if that offends but that's just the facts
* The exception is the power supply. Their are some large capacitors (big
and high capacity) that can give you quite a kick. But it isn't going to
kill you and most often you're not touching a sensitive component while
sticking your finger into the case of the power supply. In general KEEP OUT
OF THE PSU unless you have a damn good reason to be there. I learned this
from replacing CRTs in TVs decades ago. It can knock you into the wall but
you'll survive - kinda like a Taser gun. This is one case where I ended up
always running a wire from the HV connection to ground -- usually the center
prong of a grounded outlet. If I didn't see or hear a zap, I assumed the
system ground wasn't connected. That's another story.
Best of Luck!
What counts, is that all components be brought to the same potential, in
a safe manner. For example, you could unplug the computer, then put the
computer on your lap. Wear a pair of short pants, so your skin is in
contact with the case. Touch the case, to be sure you and the case are
at the same potential.
Open the antistatic bag, with RAM inside. Touch the inside of the bag
first, and not the module. The inside of the bag should have a high
resistance, but still be conducting, and any ESD discharge happens
slowly.
With memory, case, and human at the same potential, you could install
some RAM.
The reason a conducting strap is used, is to guarantee that the things
at the end of the link, are brought to a common potential. Just touching
an item, is not a guarantee it is brought to the same potential. There
is something called an electrophore, which is an insulator with a
charge on it. You can place a conductor (for example, a tin pie plate
with a wax candle as a handle) on top of an electrophore, touch the
tin pie plate, and assume it is grounded. But, if you then lift
the pie plate, and bring it near a ground, such as a cold water pipe
or the screw on a wall socket, a spark jumps over. This is
because, touching the pie plate, while it is sitting on top of
a piece of cat fur, places an "image charge" on it when the plate
is lifted away. And for this reason, you cannot assume, that simply
touching something, is a 100% solution to static. Depending on
the circumstances (such as laying the antistatic bag on top of your
cat), you could in fact pick up the RAM and zap it when it is brought
near the computer.
See page 3 here, for an experiment we did in grade school. It really works.
http://ether.sciences.free.fr/acrobatfiles/electrets/electrophore.pdf
As long as you've used reasonable precautions, to:
1) Bring things to a common potential.
2) Discharge using a high resistance path. The wrist strap provides
such a path (it is not just a piece of wire, but has a resistance).
The antistatic bag has X ohms/square of resistance, and would slow
the discharge. If you want to fast discharge something, such as
you touching the metal chassis, then that should be as safe as
zapping the computer case in real life, while you're using it.
3) Don't lay any components on top of good insulators. Don't situate
yourself in a situation you know throws sparks. For example, if
I put on a certain wool sweater, and rub my back against a wooden
chair, I've been able to throw 25KV static discharges (yes, they hurt).
Such a combination of seating arrangement, and clothing, while working on
a computer, would just be stupid. You can get some idea how bad
your environment is, by how often you're getting zapped by static
when just being in the room and touching a ground. Even taking off
that pair of insulating shoes you wear, is a start.
Connecting the setup to ground, may help if everything in the room
was grounded. For example, in my old lab, the floor was conducting
(you weren't allowed to put liquid wax on the floor, for fear of
insulating the floor), and everything in sight was connected to
ground. Wrist straps were used, and even heel straps in some of
the labs were mandatory. But a typical home scenario, is not
completely decked out in grounds, so the best you can do, is
bring everything to a common potential, as safely as you can
manage.
I've worked with some ESD sensitive components, ones where even
20 volts of static can damage them. They are so bad, that the parts
will die, while sliding down inside an antistatic plastic tube.
Current computer components have better protection than that,
and their sensitivity is probably better than 1KV HBM (human body
model). Intel USB ports, for example, have a 6KV rating, according to
an article I found on the site. Some RS-232 chips have
a 15KV rating, (which is why they don't blow up like the old 1488 and
1489 used to). But the combination of my wool sweater, and a wooden
chair, could blow any of them up.
http://en.wikipedia.org/wiki/Human_body_model
HTH,
Paul
