On Fri, 13 May 2005, Francois Robbertze wrote:

> I want to test a 2km (1.6mm dia) steel wire that runs around a 
> residential home for continuity.

You will find that steel wire has very high resistance. Expect hundreds 
of ohms or more for that distance. It also depends strongly on 
temperature.

The only way to test it I's somewhat trust would be to measure the 
resistance of each wire separately and compare them. If a strand breaks 
then you will have a serious difference in readings.

The only item I know of, that is lightning proof, is a granite boulder. 
A 2km wire is an excellent antenna. I would plan on inexpensive 
replacement modules instead of making it 'lightning proof' beyond the 
usual tranzorbs etc.

Maybe you can simply run dc through the wires and use relay logic to 
arrive at a conclusion. Relays are not lightning proof fyi. the easiest 
way for evil people to go through such a fence is to use crocodile clips 
to bridge the part that they are going to cut with cable shears before 
driving through it (with anything from a wheelbaroow to a tank).

Peter


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