I would like to ask your opinion on usefulness of TDR (Time Domain Reflectometer Cable Fault Finder).
I don't have any specific use for it now, but I've been thinking about getting one, just because :-)
I just received an email from A*I and they have the 3271 on sale with almost 80 bucks off.

Any past experiences or just random opinions on this, or another, sub $500 TDRs are welcomed.

I like the Fluke Network units .. the TS100 or TS90. The TS90 can be had for under $200.

We have used a TS90 for years, good product

Frankly, it's part of the thing that allows you to charge your rates. You can ascertain your network connections without having to trial and error it. It allows you to determine where faults lie after a wall is done.

Maybe a stupid question but can it help find a broken wire run. Specifically, a cat 5 we have on a run to the telco demarc. I'd love to show the possible location/ length where wire is broken. This particular job had some rat issues with some of the electricians wires and one of ours.
We've tried the standard toner, and even the "heavy duty" one that gets us out of a jam sometimes. Funny thing is all the other wires going to the same box test good. That's what kind of scares me. I'd love to open the dry wall before the contractor is gone.

This is part of why TDRs exist- they let you know where the breaks are without tearing anything apart.

I have a Lan Rover Tp600

[Link: amazon.com]

Maps network connections, gives distance, faults, etc....

saved me a few times in the past

A word of caution with respect to locating wiring faults. TDRs can and do permit you to do this but they also require you to enter VOP ( velocity of propagation) data in order to do the calculation. How many of you know this number in the damaged wire where you are trying to locate the break? It may get you to within 10-15 feet, which is great when you are looking at an external wire. Not nearly as useful if you're hoping to be surgical when opening a wall to repair a wire.

There are generic values for wire types but even CAT5 has slightly different VOP based on the manufacturer. A real certification tool sends 4 tones rather than 1 and doesn't need the VOP data. The inexpensive TDRs do.

One other useless bit of trivia. TDRs are much better than multi meters for testing for wire faults. Let's say you have a system where keypads are misbehaving and you do a continuity test with a multi-meter and all tests fine. Using the TDR will give you finer resolution for discovering damaged wires, even if it's only the shild and ground that are shorted.

Alan

Dave, is that a TDR as well? A quick review seems like it is not, perhaps I'm missing something. I know someone who is itching for a new LAN tester and one with built in TDR would be nice.

It will tell length, wire mapping, shorts, tone. I've never used it for more than wire mapping and lengh, but it comes in handy when needed

YES. That's why I have one.

A TDR measures the distance between where you connect it to two wires, or even with electrical stuff to one wire and the conduit ( ! ) and measures to the point where the impedance changes. We've heard that impedance mismatches make reflections; this tool exploits that, measures the time it took for the reflection, and deduces the length to that spot.

It's got adjustments for propagation velocity -- electricity is really slower than light by predictable percentages. But even if it did not have that, you could work out where something is.

Let's say you have a piece of wire that you know is 100 feet long, with a suspected break in it somewhere. You measure from one end and get 80 feet. You measure from the other end and get 30 feet. That's 110 feet, so the scale is off a bit; multiply both numbers by 100/110 to find out where the break is.


It's a bit tougher to figure out what the measurement means if there are more than one break, but you should be able to measure a known length and compare with the TDR's reading, or adjust the TDR until it's correct.


There are also different kinds of toner tests. I could describe how to check for wires that are close but not actually connected together, but it's another five paragraphs. And a TDR would solve your problem anyway.