Multifunction DAQ

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Multiple reference triggers

I am using a PXI-6123 8 channel analog in board to collect a group of 4 waveforms triggered from one channel, using a reference analog edge trigger. The trigger values alternate between 2 different slopes and levels. Since I can't load 2 different trigger values into one task and commit them on the same channel, I have to clear the task and redefine it between each acquisition. This seems to be a rather unrefined approach.

Is it possible to set up 2 tasks, each with a separate trigger channel connected in parallel to the source and share the other channels between the 2 tasks? The two tasks would be then be committed and run concurrently. The acquisition would then alternately call one of the 2 tasks.

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Hey AGC,


This might be an instance where a global virtual channel would work; however, I have never used these in my own work.  Could you post your code please so that we might see if anyone  here has any thoughts?


Cheers, Matt

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It is not possible to commit (or run) two tasks concurrently on the same device.  Even though your 6123 is a Simultaneous device with a dedicated ADC per channel, the timing and triggering engine is shared between channels so you can't acquire at different rates on multiple channels or trigger the channels independently.


Having said this, you can pre-define all of the triggering parameters and verify two different tasks ahead of time, then switch between the two tasks during the acquisition.  From my understanding of your application this should be the best way to go about accomplishing what you need.  


I went ahead and set up an example for you to start with--take a look at the following link:

Change Between Multiple Triggering Parameters on the Fly Using DAQmx



Best Regards,


John Passiak
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