How can I change the trigger delay?

[mariakand]

Hi,

my name is Maria and I am trying to perform triggered reading out of a photodiode using the PCI 6023 E card and the BNC-2090 board. I am using the example program Acquire N Scans Digital Trig.vi but I cannot find how I can change the time delay between when the trigger signal arrives and when the computer reads from the photodiode. I need to be able to vary this delay in order to get the maximum signal out of the photodiode, otherwise I average a bunch of zeroes.

I would greatly appreciate any help.

thanks,

Maria 

[Elijah_K]

Hey Maria,

Normally I would recommend the use of a counter output since you can actually specify an initial delay.  For those of you reading this who may be intereted, you would use a start trigger on the counter task and then reference the counter as your sample clock source for the acquisition task.  The counter output would not start until the initial delay had passed, which would be clocked from the moment the trigger occurs.  Using DAQmx, you can actually specify Cnt0InternalOutput as the source for the AI sample clock.

Maria, I'm afraid that your card does not support counter triggering because it is an older E series board.  In your case I believe your best option will be to disregard the samples you don't want.  It won't be any less effective than the method I described above, you'll just have unwanted samples moving across your system bus, but the result should be about the same. 

Let me know if you have any further questions.

[mariakand]

thanks a lot Elijah!

Maria