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DAQ board for acquiring analog pulses

Hi.  I'm using the USB-6251 DAQ board, and I'm trying to record analog Gaussian curve-ish pulses into LabVIEW.  Except when there is a pulse, the analog input channel is at 0V.  Right now, I've got the trigger working to start acquisition at the beginning of the pulse, but I can't figure out how to stop acquisition when the pulse is over.  I've been using the DAQ Assistant, with an Analog Window start trigger, set at the range 10m to 10 V.  Is that the right way to do it?  I can't get any reference trigger to work to stop the acquisition however.  It's set to acquire 5k inputs at 1 kHz and always goes for the full 5 seconds instead of stopping.

 

Thanks in advance for helping!

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If anyone could help me that would be great!  If my first message was confusing, please let me know and I can clarify.

 

Thanks!

 

Jeremy

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HI Jeremy,

 

So, just to clarify, are you trying to get only one pulse but right now you are getting a train of pulses?  Can you tell me a little bit about your code an perhaps attach the code itself or a screen shot? Perhaps knowing more about the code, I try to set this up here on my end.

 

Hope to hear from you!

 

Have a great day!

Regards,
Margaret Barrett
National Instruments
Applications Engineer
Digital Multimeters and LCR Meters
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Not exactly.  It's still picking up pulses separately, but it's including the empty space afterwards (as in, if the pulse lasts only 10 ms, it still acquires data for the full 1 second).  Preferably, it would stop acquiring data when the voltage is outside the analog window.

 

I attached the VI as it is right now, with just a start trigger and no reference trigger.  I'm unsure how to configure the reference trigger to have it stop the acquision once the voltage is outside the window again.

 

Thanks for your help!

 

Jeremy

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Hi Jeremy,

 

Sorry for more questions, but I'm trying to get all the necessary information to set up something similar here at my desk. Are you watching an analog input pulse that let's say is going from 0V to 5V and then back down to 0 and when it hits zero again you want to stop acquiring? Also, by stop acquiring, so you mean you want the program to stop or just the acquisition?

 

Thanks!

 

 

Regards,
Margaret Barrett
National Instruments
Applications Engineer
Digital Multimeters and LCR Meters
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Thanks for your help, although I've actually gone a slightly different route using digital signals now (which was resolved on a different thread here).

 

Jeremy

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