PXI 4472 analog trigger

[Oleks]

Hello everybody,

I am trying to get a grip on analog triggering option of PXI 4472 board. I found on this forum, few years ago, an enginner from NI reffered to the vi "Cont Acq&Graph Voltage-Int Clk-Analog Start"(attached here) as a good starting point in order to get familliar with analog trigger option for this board. The VI seems to be starightworward for my basic level of knowledge on Labview, but it seems like I am missing something.

Here is my problem, as far as I understood from the manual, I can use any of the 8 ports on 4472 as an input for analog signal that can work as a trigger. In the code, the DAQmx Start Analog Edge. vi requires trigger source "APFI0" and from the help file, it should be a virtual channel through which signal is going. I created the virtual channel named "APFI0" and connected ai0 to it, however I am getting error message:

{Error -200265 occurred at DAQmx Start Task.vi:1 Possible reason(s):

An attempt has been made to use an invalid analog trigger source.
Ensure that the trigger source you specify matches the name of the virtual
channel in the task or matches the name of a non-scannable terminal that
the device can use as an analog trigger source.
Property: Start.AnlgEdge.Src
Corresponding Value: APFI0}

I am guessing that I am not quite following how the line dedicated for triggering is initialized. On the VI fron pannel, it is mentioned that APFI0 is refered to a standard trigger pin for M-type device, which I do have (PXI 6221 with BNC 2110 block) but I did not plan to use it as an analog input.

Can anybody suggest how to approach this problem properly?

Thank you in advance,

Oleks

[MaggieAggie]

Hello Oleks, 

The 4472 does not have a PFI line, so you can't trigger off of it. Instead, write the full channel name, such as PXI1Slot3/ai0. You also need to add the channel to your task. 

[Oleks]

Hello Maggie,

Thanks for the reply! I tried to implement what you suggested but so far no luck, I guess I am missing something. I created new task "AnalogTrigger" and wired chanel ai0 to it. In MAX I saw a 1Hz sine wave that I generated externally and which I was feeding to ai0(my analog signal for falling edge). In the VI I tried both typing PXI1Slot2/ai0 in the source window and wiring DAQmxTask, while selecting my "AnalogTrigger" from the drop down menu, to the source port. In both cases I was getting exacly the same error as before.

Am I doing something wrong here?

[MaggieAggie · Accepted solution]

Hello Oleks, 

Maybe this will help. On the block diagram, make another copy of the Physical Channel list, and wire it to the Trigger Source Input on the DAQmx Trigger.vi. There will be a red coercion dot, but it will make sure you get the correct format for your trigger. 

Whichever analog channel you choose to use as a trigger, make sure it is included in the task, as in below: 

[Oleks]

Hello Maggie,

That did the trick, thank you very much!

Let me ask you one more thing if that is ok. In the current VI configuration, the analog edge triggers continuous acquisition starting at first detected zero crossing, ignoring every other zero crossing of the continuous signal through triggering port ai1. Would that be correct?

Oleks

[MaggieAggie]

Yes. The analog start trigger will trigger at the first zero crossing, then your acquisition will begin. You have not configured re-triggerable triggers, so it will only be triggered once. 

Does that answer your question? 

[Oleks]

Yep, it does! Thank you very much!