Measure cable length with a PIC?
I'm wanting to make a PIC program that can measure the length of a cable.
The idea is to be able to connect both ends of the cable to different i/o pins and have the PIC calculate how long the cable is.
I know this should be possible, as i've seen cable testers that can do it. Also, my PC's bios can tell me how long my network cable is, down to 0.1 of a meter.
Obviously sending a pulse down the cable and timing how long it takes to reach the other end is out of the question as the PIC wouldn't be anywhere near fast enough.
Does anybody know (or have any ideas) on how this can be done?
Time-domain reflectometer (TDR)
Hi Kamikaze47,
Quote:
Originally Posted by
Kamikaze47
I'm wanting to make a PIC program that can measure the length of a cable.
The idea is to be able to connect both ends of the cable to different i/o pins and have the PIC calculate how long the cable is.
I know this should be possible, as i've seen cable testers that can do it. Also, my PC's bios can tell me how long my network cable is, down to 0.1 of a meter.
Obviously sending a pulse down the cable and timing how long it takes to reach the other end is out of the question as the PIC wouldn't be anywhere near fast enough.
Does anybody know (or have any ideas) on how this can be done?
Look for:
Time-domain reflectometer (TDR)
Time-domain reflectometry (TDR)
Here is a very good DYI article using a 74AC04 hex inverter (not PIC) and your OldSillyScope.
The author mentions the timing and velocity factors that might help with your project.
QEX sample PDF article
“Build a cheap and simple time-domain reflectometer”.
Hook this up to your oscilloscope, and you can electronically measure the length of a wire to the end, or find a problem in the wire, including where the problem is physically located.
http://www.arrl.org/qex/2006/03/steinbaugh.pdf
-Adam-
