How can I check if counter input is synced with analog output?

[bfabella]

Hi,

I am working on an application for photon counting.  I am using two analog output channels on my PCI-6713 board to send a raster pattern to a set of XY scanning mirrors.  I then have a photon counting unit that emits a TTL signal whenever photons are detected as a result of this raster scan.  I am then using a USB-6211 board to count the edges on this TTL signal. 

I am having problems that I believe are due to sync issues.  I am using the AO sample clock on the PCI-6713 board as the gate for my counter on the USB-6211 board.  I am using a digital start trigger for the analog output and an arm start trigger for the counter input. Is there a way to verify that the analog output and counter input operations start at the same time and are are in sync?  I would basically like to monitor and compare the actual ao sample clock from the PCI-6713 board to the gate signal used by the USB-6211 board.  I have been able to export the AO sample clock and look at it on my oscilloscope, but not the gate signal of the USB-6211.

Thanks for your help,

Brian

[jschwartz]

Hi Brian,

What kind of problems are you running into?  Are you trying to do a buffered edge count with your 6211?  Are you trying to use your AO sample clock to take counter measurements? If not, you don't need the sample clock for the counter task.  If you are trying to use the AO sample clock, you are going to need to export the AO sample clock in this program.  You can also export the AO start trigger and start the counter task from this.  An example that might be helpful is the Synchronize Analog Output Sample Clock with TTL Pulse from the community.  

[bfabella]

Hi Jim,

I've been busy with other things so sorry about the late reply.  I am trying to do buffered edge counting, and I am trying to use the AO sample clock to take counter measurements.  I eventually did figure out that I needed to export the AO sample clock.  I will also try exporting the AO start trigger.  

From the example you posted, I noticed that the timing is specified differently.  In my vi, I have the DAQmx Timing vi set to "Sample Clock, and then I specify the source.  In the example, the DAQmx Timing vi is set to "Implicit" and the source is set using the DAQmx Channel property node.  I will try making this change in my vi, and see if it makes a difference. 

Thanks for your help,

Brian

[bfabella · Accepted solution]

Update....It turns out there was no sync problem between my counter input and analog output.  There was an impedance mismatch when I connected my photon counting unit to my USB-6211.  This was causing a variable error in the count rate.  After accouting for this mismatch, the problem went away.