"Dennis J. Murray" wrote: > I'll tell you guys - I've been following this link since it's inception and > you REALLY have my curiosity piqued!! I've used TDRs quite a bit in a past > life and I DEPENDED on the visual representation on the screen to interpret > what is really on the line! I don't think I EVER had a clean line that > didn't require some interpretation - was that hiccup a sharp bend? water in > the line? an unauthorized tap? A long-forgotten splice? etc. > > How do you plan to accomplish this using a PIC or an oscillator circuit???? > Or don't you? Just looking to determine overall length to the most > significant reflection?? In the October/November 1992 issue of Circuit Cellar, there's an article that describes a contest-winning design for a TDR that's based on an 8051. It uses a PAL and a delay line to get timing resolution down to 20 ns. See http://www.dtweed.com/circuitcellar/caj00029.htm#409 As presented, it didn't draw the waveform -- it just calculated the length and termination impedance from the height, polarity and delay of the first reflection. However, a few small changes to the design would allow capturing the full waveform. You can order back issues at Print: http://www.circuitcellar.com/products/b92_93.asp CD: http://www.circuitcellar.com/products/cd.asp -- Dave Tweed -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu