DAQ analog output missing fast triggers

[ajpeters]

I've seen this question asked a few times but haven't found a solution: I'm trying to set up a re-triggerable analog output on a NIDAQ (PCIe-6323, controlled via matlab), but after it's finished an output once it looks like there's about 100 ms of down-time before it can trigger again. The signal that I'm working with goes at 70 Hz so I need to trigger about 14 ms after it ends, which means it misses a bunch of triggers. Is there any way to trigger analog outputs more quickly?

[Shezaan]

Hey AJ, 

Are you coding this in LabVIEW by any chance, or are you programming this in MATLAB? If you are doing this in LabVIEW have you taken a look at the example provided in the link below?

Link: Retriggerable Voltage Acquisition 

https://forums.ni.com/t5/NI-DAQmx-Examples/Retriggerable-Analog-Voltage-Acquisition/gpm-p/3508185

Regards,

Shezaan Noorani 

Applications Engineer 

[ajpeters]

Thanks - sorry I'm using matlab instead - but in the block diagram is there an aspect which determines the limiting factor for time until the next trigger can be received that might be translatable to matlab? I would have guessed that it would be determined by the rate, but it seems that this isn't the case.

[Shezaan]

Hey AJ, 

I was able to find something that might help you get the functionality you are looking for. I think the page linked below describes functionality similar to something you are looking to achieve. 

LInk: Start >> More >> Delay 

http://zone.ni.com/reference/en-XX/help/370471AF-01/mxcprop/attr1856/

Let me know if this helps! 

Regards,

Shezaan Noorani 

Applications Engineer 

[ajpeters]

I think that it isn't a delay from trigger to output - the output is always exactly aligned to the trigger, it just misses triggers that occur < 100 ms after the end of the last output. 

I have a workaround for this problem that seems alright for the moment: I used to use a counter output on the daq to trigger a camera exposure and simultaneously trigger an analog output from the daq. I couldn't set the analog output to be a continuous signal because it would drift from the counter, and I couldn't trigger new analog outputs from the counter because there was a 100 ms dead time until new triggers were accepted. So what I do now is create two continuous analog outs on the same session (using matlab's daq session interface), one of which triggers the camera exposure and the other of which was the originally desired analog out, so that if they drift at least they drift together.