DAQmx Continuous Output with a Digital Trigger Read

[HeadrickJM]

Dear Forum,

I am using a PCI-6014 and Labview 8.5.1.  I have successfully made a function generator that has continuous output of a triangle wave.  What I want to do is have my DAQ board accept a digital trigger (TTL), read the instantaneous voltage of the ramping analog output, and reset the offset of the function generator to said instantaneous voltage.  In short, I am trying to make a chase circuit for the piezo of an optical cavity.

Sounds easy enough, but I am not confident in the Labview set-up.  Any help or example VI's would be helpful.

Sincerely,

Jeff

[Brian_P]

Jeff,

Thank you for using the forums.  From you description it sounds like you have an analog output task and then have a triggered anolog input task that then sets the offset for you output task.  From this description it sounds like you want to perform this multiple times and thus have a retriggerable anolog input.  I have found a knowledgebase article that deals with exactly this issue.  There is also an example in this knowledgebase article that is call retriggerable ai with a retriggerable counter.  I believe this is exactly what you are looking for.  You can then run this example in parrallel with your function generator.

In order to reset the offset of the function generator, I would use the reading of the input and then read that back into the offset.  If you wanted to set an initial offset, I would suggest using a case structure, so the first time, it runs the initial value and then all subsequent times it would run whatever value that you had read previously.

I hope that this helps.

Regards,

Brian P. 

[HeadrickJM]

Dear Brian,

This is basically the same solution I came up with last night...sadly, I was hoping for something a little more sexy.  My gut told me I shouldn't have to consume an analog input channel to find out what voltage the analog output channel is at when the board recieves a digital trigger.  However, it seems like this is how it has to go...

Sincerely,

Jeff