TDR Measurement using PCI-6251

[erwade_mit]

Hello ... i am interested in using my current setup (PCI-6251 and BNC 2110 connector block) to make a time domain reflectometer (TDR). I read the tutorial 'How Do I Perform Time Domain Reflectometry (TDR) Analysis Using NI Products?' but do not have money to purchase new products.

I am interested in obtaining characteristic impedance for small transmission lines. Does anyone have any experience building a TDR in software using a standard multifunction board? I would be very interested in some help with this. Thanks.

[Kenn_N]

Although I don't see why it wouldn't work, you wouldn't have the same amount of accuracy.  Using the Cable Fault detection vi's as a place to begin you can use DAQmx for all the hardware calls.  Simply generate a square wave on your counter and continuously read in on an analog channel.

Good Luck

[erwade_mit]

Thanks for the reply ... I have in fact worked on it, and it is just a question of resolution. Thanks!

[gwd]

The PCI-6251 is a rqther slow (1.25 Ms/sec sampling rate) unit.

For TDR you need (pulse rise time)*(velocity of light) << (length of the transmission line being investigated). This will not be the case unless you are working with VERY long cables.