trigger and gate - how to change the number of samples for the stop trigger

[Stojac]

Hi,

Is it possible to change the number of samples for the stop trigger from the front panel? I have found several post of a similar topic, however with no answer to my question.

What I want to do is to stop the trigger after a given time. Of course the number of samples for the stop trigger condition depends in that case on the sampling rate...

I appreciated any kind of help.

[DavidVr]

Dear Stojac,

 I'm not quite sure on what you want to achieve with stop trigger. Is this trigger a physical digital edge that you want to use? What do you exactly mean about number of samples of stop trigger? What particular device are you using? Triggering possibilities vary depending on you chose E- Series, M-Series or X-Series. Maybe the best way I would understand your application if you could draw a diagram with triggers and samples to acquire. Can you please do something like that and can you please explain more in depth the goals you want to achieve!

Thanks!

Best,

David Varga

NIH

[Stojac]

Hi DavidVr,

   Thank you for you interest and sorry for me being so vague about what I want to achieve - I just didn't want to go into details to deep. Anyway, I use USB-6251 DAQ for one analogue input signal acquisition. To be more precise, to that input a Genius communication bus is connected. I try to register and analyze the communication process. On that analogue input I get characters sent through the communication bus. Every character has of course a constant length in the means of time. I just wondered if it is possible to change the sampling rate of that analogue input "on the run" and depending on the sampling rate change the Triggered Signal length (defined with the number of samples of stop trigger condition).

   Is my explanation any good? If there is anything still unclear please ask.

You ask me about some diagram... Please see another post I've started (about "Genius network communication process registration").

http://forums.ni.com/t5/LabVIEW/Genius-network-communication-process-registration/td-p/1438326

There is attached a VI for Genius communication analysis mentioned above (in the archive file "01 Acquisition.vi"). At this time as the input I use HWS file, but I want to develop it later so that the waveform was from analogue input directly (now I use Signal Express for the signal acquisition).

Best regards,

Jacek

[DavidVr]

Hey Jacek,

  Yes the explanation is way better 🙂 I think we have an example code on the web that almost satisfies your needs:

http://decibel.ni.com/content/docs/DOC-5311

The only problem is changing the AI sample rate on the fly. The analog input does not allow to change this frequency while the task is running, so we will trick it by changing the freq of the CO task that is preparing us the sample clock:

Please try to put togather the code, I'm pretty shure it will wotk for you and this is what you are looking for!

let me know if you have further questions!

Best,

David Varga

NIH

[Stojac]

Thank You for the example code. I have to think it over. At first it seemed to be complicated as I do not have much practice in LabView, but I think I will cope with that 😉 If only I had more time - recent days are very busy 🙂 First of all I have to find out what is the PFI line - yes, my knowledge is this small 😉 Thanks again.

Do You have any suggestions or hints on the other topic (http://forums.ni.com/t5/LabVIEW/Genius-network-communication-process-registration/m-p/1440218)?

Regards,

Jacek