Simple circuit to turn your oscilloscope into a TDR

Posted on Tuesday, March 12th, 2013 in oscilloscope by DP


Simple circuit to turn your oscilloscope into a TDR:

This simple circuit allows you to use your oscilloscope as a Time Domain Reflectometer (TDR). This is how it works. Send a pulse down a cable and watch for the reflection. Most people think a TDR is more complicated than this. Your oscilloscope is used to sample and view the reflected waveform.  In this circuit we use the 74HC4040 counter to create the length of the pulse we will send down the cable. Build this inexpensive circuit and now you will have a TDR.

Via Electronics Lab.

This entry was posted on Tuesday, March 12th, 2013 at 9:00 pm and is filed under oscilloscope. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.

One Response to “Simple circuit to turn your oscilloscope into a TDR”

  1. Popol says:

    I use an OTDR everyday to troubleshoot troubles on fiber optic networks. Those are quite useful to pinpoint exact locations of events over a large distance.

    I’d think this circuit would be pretty obsolete if you’re looking for a trouble on a short range. It would be more usefull for copper cables over 100ft, to find impedance mismatch, break, etc. For shorter range, you’d need to add a known length buffer cable before (or trick the end with an impedance mismatch to see an event, and put a marker)

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