usb 6218 slow digital trigger of analog reads

[juanni]

All,

    I specifically bought (several years ago) a usb 6218 so that I could do triggered data acquisition.  Specifically, I want to read my boxcar integrator's output every time it is triggered.  I have a nice digital signal to trigger the usb6218.  The idea is, I hit run on the Labview vi, click the acquire button on my 3rd party software (ICCD camera), then my laser triggers 9-11 times (there is some variation) in the course of the acquisition.  The boxcar needs to make a new measurement after every laser shot;  I want the usb 6218 to read the boxcar output after every shot and return an array of the 9-12 readings.  I truly have no idea how to start with this in spite of years of labview experience... I am finding that my labview experience does not help me with DAQ.  Any help (which tutorial to read, what daqmx configuration to use, etc) is appreciated.  J  

[Hey.itsDale]

Hi juanni,

It sounds like what would help you is a re-triggerable analog input task. There is some useful information and examples linked at the bottom of this page:

http://www.ni.com/tutorial/5382/en/

Specifically this example:

http://www.ni.com/example/27345/en/

The main idea is to use the counters (the 6218 should have two internal counters) to generate a finite pulse train when digtially triggered. Then the analog input task uses this pulse train as its sampling clock (samples are taken on rising edges of the pulse train). You would need to specifiy how many samples you would like to take after each trigger.

[xband]

HI,

I'm trying to do a very similar task.  I want to externally trigger the USB- X series 63x1, from the PFI5 channel, causing AI acquisition which are then used in a PID loop.  If a threshold is exeeded we then send a pulse train from the Counter ct0. 

I"m confused about the "Re-Trigger" wording.  Do I need to use my external trigger to trigger the internal clock for AI acquisition?  I want to send a limited number of pulses as a result of the PID calculation.  Can the Counter be config\ured similarly? 

I keep having errors that the acquisition did not complete. 

Any help is appreciated, I responed here since this is a recent post.

Thenks,

JIm

[juanni]

Jim,

     Can you even get your DAQ task to read under any external trigger situation?  It took me a while, but I can get it to trigger under some limited situations, but have some new problems:

http://forums.ni.com/t5/Multifunction-DAQ/read-all-available-samples-not-working/m-p/3302205#M89531

J

[xband]

It seems to run.

Currently I"m trying to configure an AO channel to measure on a scope against my trigger.

[xband]

I ended up using a "commit Task" vi in the Daqmx toolbox, there was a randome reference I ran across, I"ll try to find it again and post it.

Now I"m wondering if a "pause trigger" is a better solution.