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Multiple channel trigger



I am trying to make signal aquisition using the board NI-9234, but I am having trouble for set the trigger. I am using different sensors in the input. In the first channel I am reading voltage and the other three channels I have microphones, so I am reading sound pressure. My source to the trigger is the voltage input, and I need to record all four channel simultaneously (with the same rate) after the trigger is actived.


I was trying to do that with the Signal Express, but I do not think it is possible, I cannot make both the voltage and the sound pressure signal with the same trigger. Now I am trying with the LabVIEW...


Thank you


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Message 1 of 6

What is "the trigger"?  Is the 9234 something that plugs into a cDAQ or a cRIO?  Where does the timing come from?  I don't understand using one channel for "voltage" and the other three for "microphones" -- all four channels are A/D (voltage) channels ...


Have you tried playing with your device in MAX?  You should be able to set up a multi-channel DAQ Task, including defining the Timing and Triggering.  Once you can do that in MAX, it's generally very simple to do the same thing in DAQmx.


Bob Schor

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Message 2 of 6

I have attached my VI. It is slightly different from the one I had mentioned above, but the problem is the same. I can't set properly the trigger. The following error appears:


Error -200077 occurred at Property Node DAQmx Trigger (arg 1) in DAQmx Start Trigger (Analog Edge).vi:7160001->Medição de

Possible reason(s):

Requested value is not a supported value for this property. The property value may be invalid because it conflicts with another property.

Property: Start.TrigType
Requested Value: Analog Edge
Possible Values: None

Task Name: _unnamedTask<1B2AE>



If I 'pass-by' the trigger, the acquisition works fine.

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Message 3 of 6

It looks like "Martelo" is the device whose A/D you are trying to trigger.  I don't know what kind of device this is, so I can't look up whether or not it has the possibility of being triggered by an Analog Edge (the fact that you get an error message suggests not).  I assume you know the Error Wire connected Start Analog Edge to Start Task is missing, right?


Oops -- I just noticed that Martelo is not the device, but a designation of the Channel(s) for something (Force IEPE?) -- the Task Input to the first DAQmx VI is unwired!!!  So you are sending commands to no device!  Put a Task Constant in there, right-click it, and see if your Device shows up (it should if you've connected it while MAX is running so that MAX "sees" it).


Bob Schor



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Message 4 of 6

Hi, Bob Schor


Thank you for the answer. 

The Task Input of the DAQmx Create Virtual Channel don't need to be specified. If it is not, the LabVIEW creates the task  (

The "Martelo" is a Impact Hammer. The idea is the trigger to activate when I hit with the hammer. Then I can calculate the FRF using also the signal from a accelerometer (both the hammer and the accelerometer are IEPE). But each average from the FRF should be take into account only after the system identify a trigger.


I couldn't run the VI again, because I don't have the board A/D with me right now. But as I said before, if I delete the DAQmx Start Trigger, the VI runs fine. For this reason, I believe the problem is occuring in this step. (The error wire was missing so that I could copy the error message). I also tried to remove the while loop, but the error remains.



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Message 5 of 6

The same error appears with other examples I found in this forum. (Another example is attached)

The only information I found about the triggering with NI 9234 (C series) is that the trigger channel must be the first channel from the board. But still, it does not work...

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