I need to acquire data from 5 channels on two PCI-6110 boards simultaneously.

[Ryan_V[DE]]

Taylor,

What exactly is not working about the application? Are you getting an error? I don't have two Traditional DAQ-compatible cards in my machine, but can get them if necessary. Is the master device triggering? There was data in the graphs of the VI that you attached. What does this data represent? It looks like both boards were able to read back the same 2 volt signal at the same time.

Thanks,

[Taylor]

Well, the vi is running and acquiring data, but it is not waiting on the analog trigger.  Right now I just have a battery hooked up to a switch and wired into both devices, so I am sending one channel on each device the same signal.  The data in the window is where I hit the switch twice, thus giving two pulses.  When I click to run the VI, it immediately begins recording, it doesn't seem to be waiting on the analog trigger, even though I have the wiring as it is now.

[Ryan_V[DE]]

Taylor,

I think the problem may be that you don't have the read position set to "relative to trigger point" in the AI Read VI. Please have a look at the Acquire N Scans Analog Hardware Trig.vi example program available in the LabVIEW example finder (Help->Find Examples). You will need to set this parameter in both reads. Good luck!

Regards,

[Taylor]

Well, I did that, but here is what happens, I guess the AI Start is synchronous between the two devices but the AI Read is not.  The master device gets the trigger, reads/plots/saves the data, then the slave device waits on another trigger to read and acquire data.  If the slave device doesn't get the trigger, it times out.

-Taylor

[Ryan_V[DE]]

Taylor,

I got another Traditional DAQ board in my machine. After modifying your VI to set the read position to "relative to trigger point," it ran as expected. Do you physically have the two cards wired together with a RTSI cable?

Regards,

[Taylor]

Hey, I really appreciate your help on this, I'm not sure why it is giving so much trouble.  I am certain that the RTSI cable is installed.  I checked it visually, but also I took the analog triggering parameters out of my VI and both channels acquired synchronously.  I will upload another copy of the VI with the "relative to trigger point" set.  If you open it, you will see in the two graph windows what is happening.  One device receives trigger and acquires, then the other device recieves trigger and acquires. 

Thanks again,

Taylor

[Ryan_V[DE]]

Taylor,

I just noticed that you don't have the pretrigger scans connected to the slave AI Start. This will cause the alignment problems that you are seeing.  I didn't see any problems because I didn't actually have anythhing connected Do you need any pretriggering? I would suggest that you not worry about it unless necessary. If you do, then wire this control to the AI Start of the slave device. Please let me know if this helps.

Good luck,

[Taylor]

The AI Start on the slave device is still waiting on the master device to finish acquiring.  So in the current setup, once the master device acquires data, the slave waits on a new trigger and acquires a completely different signal.  It just doesn't make sense because this VI is just a modified version of the example VI Two E-series Shared Digital Trigger.  When I open this example VI it acquires the data perfectly and synchronously, but when I modify it for the analog trigger, it starts giving this problem.

[Taylor]

Ok, so I took the pretriggering out of it all together, and it behaves as I want it to.  Both devices start simultaneously once the analog trigger conditions are met.  Pretriggering is not absolutely necessary but it would be a good thing to have for this application.  Why would pretriggering cause the devices to not acquire at the same time? 

Thanks,

Taylor

[Taylor]

Well, I went ahead and wired up my actual sensors to the DAQ board and ran a few tests with all channels acquiring.  It looks like it is going to be really important to get this pretrigger scans working so that I can grab some data points just prior to the trigger.  Let me know if there you've come up with any ideas as to what is causing the pretrigger not to work properly.

Thanks,

Taylor