Trigger restarts on DAQ board

Question

Hi.
I'm doing data acquisition with a DAQ board, the USB-6251 model.  I need something like the sample VI "Acq&Graph Voltage-Int Clk-HW Trig Restarts.vi", except I need the trigger to restart much more efficiently.  When I run that sample VI (and my own adaptation which is attached) I can only get trigger rates of about 30 Hz, and trigger that comes in within 30 ms of the previous one is just ignored.  I need it to handle trigger rates of up to 1 kHz. Does anyone have any ideas, or is there another way to go about it that will avoid this problem?
Thanks,
Jeremy
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Attachments:
Restarting trigger.vi ‏25 KB

Answer 1

I think to get the response you want, you will have to use your Trigger signal to start generate the correct number of clock signals from a Counter.  See example 'Gen Dig Pulse Train-Finite-Retriggerable.vi'
Use Example 'Cont Acq&Graph Voltage-Ext Clk.vi' to actually do the acquisition.
For a test, set up as follows:
Set the Rate/Frequency to the same value.
Set the Number of Pulses/Samples to Read to the same value.
Set the Counter(s)/Clock Source to the same source
For the Gen Dig Pulse Train-Finite-Retriggerable.vi set Counter(s) to ctr0
For the Cont Acq&Graph Voltage-Ext Clk.vi set the Clock Source to Ctr0Out
Run the Cont Acq&Graph Voltage-Ext Clk.vi first and then quickly start the Gen Dig Pulse Train-Finite-Retriggerable.vi
You should see the acquired signal from whatever input you have connected.  I was able to do this without changing either example program.  Once you see it work, you can combine the two into one vi.
Message Edited by rpursley8 on 07-07-2009 04:19 PM
Randall Pursley