21 Jun
2005
21 Jun
'05
11:11 a.m.
Paul Koning wrote:
Usually not too hard to get fixed, if you talk to the right
person. Sometimes it's hard to find the right person.
(ie. phb: "sounds expensive, we'll just work around it")
However, you first have to discover the problem. It's
rare enough that it's not something you usually check for,
unless it's causing problems.
Until you can get it fixed, you still have to deal with the
problem in the meantime, or suffer more damaged
equipment. You unplug it, people will say "we need
this" and plug it back in. (Hint: to keep something
unplugged, turn it upside down and open a random
panel or two, or remove the cover. Scares them off
for a while. An oscilloscope nearby helps too, even if
it's just plugged into it's own square wave generator.)
Cables between two buildings are usually not going
to get the building grounds joined. You then need to do
something to work around it (opto-isolate, optical
fiber, radio/microwave, etc)
>>>>"Kevin" == Kevin Handy <kth at srv.net> writes:
>>>>
>>>>
Kevin> Grounds are usually local to the building they are in.
Kevin> Grounds are often done using a metal post hammered into the
Kevin> ground (hence the name). The ground is not supplied by the
Kevin> power company. Two buildings can each be properly grounded,
Kevin> but their grounds can be at different voltage levels.
Certainly.
Kevin> Sometimes one building may have two different grounds. It gets
Kevin> fun where the outlets in one wall are grounded to one side of
Kevin> the building, and another wall is grounded to the other
Kevin> side. It's a good way to fry equipment.
More importantly, it's a hazard to people. And it's a violation of
the electric code. Yes it happens, and my point applies: you'd want
to fix it before someone gets hurt.
I remember hearing that this happened at one of
DEC's buildings, and
one of the computer rooms had this wiring issue. It melted the big
"welding cable" ground straps that are used on RP04 class disk drive
cabinets.
Yes, you can get an amazing amount of power out of
it in some cases, but it's not reliable enough to expect
to power anything with it. You usually need an
electrical storm nearby to cause a gradient.