From: Mark Holm 
To: atm{at}shore.net, atmer{at}flash.net
Reply-To: Mark Holm 


How about PVC conduit.  I have never worked with it, only PVC pipe, but I
can see a couple of advantages for an in ground installation.

1. no rust.

2. If the fittings can be glued together as with PVC pipe, then it should
be possible to keep water out of it.  Just don't leave the outside end
pointing up.
  Put a couple of elbows on the outside end so it points down.

I would much rather have only low voltage going out to the scope if at all
possible for safety's sake.  Nothing higher than 30 volts.

A long run of data cable in metal conduit may not work out well, especially
Ethernet.  Also a long run of data cable in close proximity to another
cable may
have problems.

As I recall, the maximum run for parallel printer cables isn't all that
long. It has been a while since I read up on that sort of thing.

Use a heavy gauge wire for your low voltage supply.  Use 12 gauge just as if you
were running a 15 - 20 amp 120 volt circuit.  Smaller gauge is asking for
voltage drop problems.  You can get 12 gauge single wires at any building
supply
or hardware store.

Run at least one extra 12 gauge wire for a dedicated ground, separate from
your power source ground.  It may well come in handy to be able to ground
everything in your system to a common ground.  Often solves a number of
ills.

To help get the wires through the conduit buy a quart of cable pulling
lubricant.  The brand I am familiar with is Ideal 77.  It is simply slimy
water based gel that helps the cables slide through the conduit.  Also buy
some sturdy
nylon seine twine.  Put it in the conduit as you install it and you won't need a
fish tape.  When you pull in the cables, pull in an extra length of twine at the
same time.  Then, if you have room, and want to pull in another cable at a later
date, you have the means to do it.

Mark Holm
mdholm{at}telerama.com

--- BBBS/NT v4.01 Flag-4