Trigger Holdoff for the 5122?

[RJM2]

A quick question about the Trigger holdoff on the NI-5122.

I've been fiddling with the value (I'm assuming it is in seconds), but find that despite setting it to even a high value (such as 2 seconds), I am able to trigger it every half second.

Any ideas?

Thanks much,

Russ

[minh.tran@ni.com]

Good morning Russ,

Thanks for contacting National Instruments with your issue, we'll try our best to resolve it for you as quickly and efficiently as possible.

To eliminate as many variables as possible, try working from one of our example programs.  My recommendation would be to use the niScope Configured Acquisition.vi example.  You can find it by going to Help > Find Examples in LabVIEW and then navigating to Hardware Input and Output > Modular Instruments > NI-SCOPE > Demos.

You can then modify this code by clicking the edge and expanding that very first NI Scope Property Node and creating a control for the Trigger Holdoff.  There should be no problems increasing the trigger hold-off for your NI-5122 well past 2 seconds, the specifications indicate you should be able to go to 171.79 seconds.

Sincerely,

Minh Tran
Applications Engineering
National Instruments

[RJM2]

Hi Minh,

Thanks for the quick reply.  I've looked at the example code, and added a Trigger Holdoff to it.  I am still unable to force the card to wait after beginning an initial trigger.  The Trigger Delay works, but I can't get the Trigger Holdoff to.

Any ideas as to what I'm doing wrong?

Thanks,

Russ

[RJM2]

Hi Minh, sorry, I think I found the problem.  That is that I'm not using Multi-waveform fetch.  I'm only fetching one waveform (cluster) at a time.  If I want to use multi-waveform, does this mean that it will capture 2 (or more) different waveforms at two successive trigger times?  If I'd like to implement this, what is the best way to display the most current waveform (I'd like to be able to display the current waveform and not wait for the entire fetch to complete).

Thanks,

Russ

[minh.tran@ni.com]

Good afternoon Russ,

I am not totally clear on what you're trying to accomplish, but I'll explain the concept behind multi-record acquisition and how to implement it and hopefully it will have some relevance to your issue.

The idea with multi-record acquisition is that instead of requiring communication with your PC (or PXI controller) to tell the digitizer/scope to re-arm its trigger after it's capture its first record (of a certain number of samples), it automatically rearms itself completely in the hardware domain.  It stores each new successive record in a new location in memory, which can be fetched off into the PC memory while new acquisitions are occuring and new records being written to memory. 

In order to always display the most current waveform captured, just ensure before you call an niScope fetch function, you have a property node with the value for Records Done property wired to the Fetch Record Number Property.  There are several good multi-record acquisition examples you can look at if you go to Help > Find Examples > Hardware Input and Output > Modular Instruments > NI Scope and then Continuous Acquisition.

Best of luck.

Sincerely,
Minh Tran
Applications Engineering
National Instruments

[craige]

Unfortunately, in my own quest for triggered acquisition I'm finding that some acquisition cards don't allow Trigger Delay and Trigger Hold off at the same time. Make sure Delay is 0 or not wired when attempting to apply a trigger holdoff.

Also, make sure an error isn't being returned from niScope Configure Trigger .vi.

Craig