Paul Kierstead wrote:
snip
- It isn't about working on the mains, but about accidents that happen.
A power supply might be plugged in and wired incorrectly, for example.
The oddest things happen. I remember working on a darkroom timer
(digital) once; it had the grounding plug cut off and was wired with the
neutral to the case. The plug was in upside down and I got quite a jolt
from the *case* (this is why it was being serviced). If I had a
non-resistive wrist strap on, the unpleasant experience could have
become a fatal one. Rule one of working with power: Accidents happen.
- The resistor limits current a lot. Lets say your body is zero
resistance; a 5 megaohm resistor will limit current to microamps. It
does'nt have to "take" current; it limits the current simply (consult
ohm's law).
- Of course if you have a hand on a ground and touch the other to the
mains, you are in trouble. The point is for the wrist strap not to add
*new* problems; it doesn't solve old ones. That is why the resistor is
there. Again, consult ohms law. Note on really high power stuff, they
trained us initially to put one hand in our back pocket to stop us from
doing stupid things. Here is something to think about: Lean up against a
table or other waist high item; what part touches the table? That is why
you see some techs with their ass stuck well out

Again, you are missing the point a bit about the wrist strap. Yes, it is
to provide protection against static. However, having a ground around
your wrist introduces *new* health hazards, i.e. an increased chance of
electrocution. The resistor mitigates this risk.

That was an excellent explanation, Paul.

Of course, the resistor is only a good idea for those of us that
don't plan our accidents far enough in advance to remove the wrist
strap prior to accidentally contacting operating voltages.

R,
Tom Q.