Hi Mike,
There are several ways to do this. The one I like is re-triggerable and will acquire as long as trigger is active.
1. Setup a Continous Pulse Train with a Pause Trigger (Counter 0)
2. Setup a Cont Acquisition with External Clock Source (Internal Output of Counter 0)
3. Physically configure your logic enable pulse to a PFI line, set the Pause trigger to that PFI line. I tested using PFI 0.
I used two examples to test this: Gen Dig Pulse Train-Continous-Pause Trigger for the pulse train generation and Cont Acq&Graph Voltage-Ext Clk for the acquisition. These two examples ship with LabVIEW and will work with your NI 6250.
The behaviour is when the Pause Trigger is active (can be active high or active low) then the Counter is generating a pulse train. The data acquisition code is waiting for a sample clock, we set the source of the sample clock to be the Counter internal output. The the period of the active Pause trigger then data acquisition is occuring.
Please let me know if you have problems implementing this, it should work very well. The main caveat you want to be aware of is setting the number of samples to read to a appropriate number, set the clock rate of the data acquisition to the same as the counter pulse train rate and the timeout on the DAQmx Read to a appropriate number (-1 is infinite).
Best regards,
MatthewW
Applications Engineer
National Instruments
Message Edited by Matthew W on
12-04-2007 11:28 AM
