04-16-2007 07:54 AM
04-16-2007 05:17 PM
Larry,
There should not be a problem using a counter to trigger
your analog input, as KB 3LDIORN5
lets us know that pulse generation can be done. You can also use a digital
channel as the counter trigger, therefore saving your analog channels for other
measurements. You may also check that you have DAQmx Base 2.1, and not an
earlier version.
04-16-2007 10:45 PM
David,
Thanks for your response.
I guess I was looking for a little more information. I am new to Daqmx Base and do not know all the ins and outs. I was hoping you could point me towards an example in Daqmx Base that might help me out.
Let me clarify what I am trying to do.
I would like to acquire a finite amount of analog data triggered by an analog trigger which is connected to the APFI0 channel.
Using the Start and Stop Tasks within a loop cannot keep up with the triggers therefore I have read that I need to use a counter which is retriggerable to trigger the analog input.
I realize that counter pulse generation can be performed, what I can’t figure out is what I should be using as the source for the counter trigger. It appears that the counter trigger has to be a digital trigger. In some examples I have seen in Daqmx they are using the Analog Comparison Event or the AI Start Trigger as the counter trigger. Looking at the trigger.vi it appears that they can not be used as a clock source in Base.
This post (http://forums.ni.com/ni/board/message?board.id=170&message.id=189503#M189503) suggests using a dummy analog output in order to initiate an Analog Comparison Event to trigger the counter. But again the Analog Comparison Event is not an available trigger source for the counter in Daqmx Base.
It is also not clear how to program the counter to be retriggerable. In Daqmx there are property nodes for this but not in Base. I have not found any vi that sets the counter to be retriggerable.
You state that I could also use a digital channel as the counter trigger. I am not sure if you are suggesting that I add hardware which would detect the analog trigger and output a digital trigger or if you’re suggesting some sort of routing scheme.
Thanks for your help.
Larry