PXI-5105 Triggering delay problem

[TCUENGR]

Hi there,

I'm running the PXI-5105 (12Bit 8Ch @ 60Msa/s/ch) using the attached VI. I have it set to trigger off of Channel 0 at 1V.  When I put in a 5-cycle sinusoidal waveform, it seems that the scope triggers too late and I only see 4 of the 5 cycles.  I confirmed this by generating an increasing amplitude sinisoid through a PXI-5412 and again the waveform was truncated, as if there was a delay after the trigger hit.  (btw, I've got an oscilloscope running in parralel and the waveforms show up perfectly there) 

Any help on why this is happening would be truly appreciated.

Thanks!

[Dustin_D]

Hi TCUENGR,

Can you give me some details of your 5-cycle signal?  Are you looking for five cycles?  Does it just contain five cycles?  What is the frequency of the cycles?  What is the amplitude and Also can you include your code for generating your test, that would be helpful for me to understand your problem.  Thanks!

Regards,

[Austin_W]

Hello TCUENGR,

I noticed that the Reference Position property in your VI is set to "0.0".  This means you're not capturing any pre-trigger samples.  Is this the behavior you intended?

Austin W.

National Instruments

[kmcdevitt]

Hi,

Our PXI-5105 was involved in a recall.  Did you get the "Long Term Fuse Reliability" recall letter from NI?

Kevin. 

[TCUENGR]

Thanks for all the replies!

Dustin - I'm inputting a .5Meg 5 cycle sinusoidal burst at an amplitude >3Vpk-pk (not always the same).  I don't have the code for generating the burst with me on this computer though I can post it at a later date if it could be useful to diagnosing the problem.

Austin - Thank you! Kudos for pointing that out as I initially thought that particular property controls something different, though after some research it did allow us to capture the whole signal we were looking for.

Kevin - The 5105 unit we have is relatively new (since late Jan) so I doubt it may be a part of the recall but I'll definitely check on that.  

All in all it seems a part of my problem is solved by Austin's suggestion, but I'm still having issues with the triggering.

At the moment it seems that I can't trigger at a level <1V.  The digitizer simply doesn't recognise it and will time out.  e.g. if I put in a trigger of 500mV and a signal of 600mV.

Any ideas?

Thanks very much for all your help!

[Dustin_D]

TCUENGR,

Can you reproduce that behavior with the ni-Scope Soft Front Panel? 

Regards, 

[TCUENGR · Accepted solution]

Actually - problem solved.

When I was playing around with it I had inadvertantly set it to DC coupling.  AC coupling fixed it.