2 triggers with PCI 5124

[Adrian_Bradu]

Hello,

I would really appreciate if you could give me some advise on triggering the acquisition of my digitizer NI 5124.

Basically, what I am trying to do is the following:

1. Perform a triggered acquisition (using an analog edge trigger). My signal goes in CHANNEL1, the trigger (TTL) goes into the external trigger input. It works beautifully.

2. Do a multirecord acqusition. It works great as well. The result after "niScope MultiFetch Binary.vi" is a 2d array, which I convert into an image.

3. The problem is that I want to start the acquision of my "image" (of my multirecord acquisition) using another trigger (at around 2Hz) (my first recording has to be synchronized with my external trigger).

I am quite sure that this is not an unknown problem, but unfortunately I am not "smart" enough to sort it out myself ...

Thanks a lot.

Adrian

[dansch]

Hi Adrian,

So currently, you are using a reference trigger on the external trigger input. When you say you would also like a start trigger, do you mean just a single trigger at the beginning to arm the digitizer? Or does each record need to be armed by this additional trigger at 2 Hz (basically, an advance trigger)? Both of these can be implemented using property nodes (found under Synchronization category) and configuring the source to be a PFI line (the same line for each or different ones).

I am somewhat confused by the need for a "start" trigger and how it is different from your current setup. Perhaps you can provide more details on the signal and the need for the "first recording to be synchronized with the external trigger". Thanks, and I look forward to hearing back soon!

[Adrian_Bradu]

Thanks for your reply. The image bellow shows I hope clearer what I want ..... My second trigger needs to start my multirecord  acquisition. It's a problem similar to this: http://forums.ni.com/ni/board/message?board.id=150&message.id=2925&requireLogin=False

Unfortunately I  couldn't sort it out ...

Adrian 

[dansch · Accepted solution]

Hi Adrian,

Thanks for the clarification. Is your faster trigger (the reference trigger) synchronous to the slower trigger which you wish to begin your acquisition on? In the example I posted on the other forum post, you can see that a normal reference trigger is configured, but I also included a property node to set the Start trigger source to be PFI 0. Thus, the digitizer will not arm itself and start acquiring pre-trigger samples until the trigger is sensed on the PFI 0 line. This would be the slower, second trigger in your case. The digitizer will not start acquiring records off the faster signal until that slower trigger occurs. Of course, if the two trigger signals are exactly aligned, you may miss the very first edge (line 1) since the digitizer was just being armed, but you could account for that type of situation by adjusting the trigger to occur on a rising/falling edge and taking more or less pre-trigger samples.

Is there anything else in particular regarding the other post or the example that I gave which I can help to better explain?

Regards,