Proper use of the Impulse Response Pt by Pt function

[jessieb]

I am having some trouble with the impulse response VI.  When generating signals in the software I am getting the expected output from the VI.  When feeding the same signal captured through 2 analog acquistion cards (either a short from the generator to the 2 inputs, or the output of a DUT sent to 2 channels) the VI also produces the expected output (~1 at index 0).  However when the signals at the stimulus and response inputs are not exactly the same the VI is giving results that are both obviously incorrect and grossly inconsistent. One obvious issue is that even when a delay is plainly present in the signals the only value that is not negligibly close to 0 is ALWAYS at index 0 where I expect the delay to show up in the impulse response.  Shown below are the data fed to the stimulus and response inputs of the impulse response VI:

And now we have the output of the impulse response VI:

The value at index 0 of the impulse response seems reasonable here but as I mentioned if I run the measurement multiple times the output is inconsistent.  And there is obvious dealy in the time data and I would expect there to be values at index's other than 0 in the output of the impulse response VI.

Is there something I dont understand about what I'm attempting here?  I am using an MLS waveform generator VI as the input to the DUT.  Thanks

[LocalDSP]

Please attach VIs or at least data (input and output) so we can reproduce your problem.

Screenshots are not very useful especially when they mainly look like white rectangles.

MLS stimulus info could also be helpful. What is your DUT and what impulse response were you expecting?