Originally Posted by Dockhead
I wonder how many kilometers of coax, Cat5, twisted pairs, and paired-wire cable I have on board. I think an investment $200 for a purpose-made TDR, and a Fluke no less, is perfectly justifiable on my boat (acquistion of new tools seems to always find some justification or another
). I only wish I had had it last May
It would have saved me hours and days of faffing about.
I don't have an oscilloscope and have no (apparent) need for one, so that's out as a substitute.
When I first read your post about buying
the Fluke cable tester, I was going to suggest something very similar to what Paul Elliot posted for several reasons.
1. I'm not a huge fan of Fluke equipment
. I also don't buy Snap-On or Mac tools, generally speaking I think they're overpriced compared to other quality brands. I have a $35 DMM that is a Chinese copy of a Fluke 87v. A coworker had just bought a Fluke for over $350 and we had to send them both in to the Navy's cal
lab for calibration prior to use. Mine came back calibrated, his Fluke which cost 10x more, came back as "unable to cal
." Normally I'll spend the extra money
to get higher quality, but we often saw that isn't what you get. He did get it replaced, but it had the exact same functions and identical precision and accuracy as mine for 10x the price
2. The major benefit of a TDR is not so much it's ability to measure the distance to opens/shorts, it gives you a visual indication of the impedance mismatch at the connection, caused by a poor crimp, poor solder joint or corrosion
. The Fluke cable tester is like a pair of smudged reading glasses compared to a microscope.
3. My suggestion would be to spend around $200-300 to buy either a used oscope on Ebay (Agilent (formerly HP), Tektronix, BK Precision are all good brands) with at least 200 or 300MHz bandwidth, the higher the better. There are also small portable digital "pocket scopes" in that same price
range, but I don't know enough about any of them to recommend any. With an o'scope, you'll be able to isolate and track signals that no DMM can see, troubleshoot to a level far beyond "go/no go."
4. Then build yourself an "octopus" to go along with your o'scope. I built mine for about $20 and it's invaluable. It allows power off in-circuit testing of any component and will tell you if that cap really is holding a charge or filtering that signal, or if that resistor is still 220K ohms. Here's a link to building and using one: Davidson College Instrumentation Specialist - Physics - Octopus
For only $50-$100 more than the Fluke, you'll be getting 10x the capability for a much wider range of uses.