How do I acquire multiple signals in the NI cDAQ 9172 using 2 analog input modules?

[Jud~]

Hi everyone,

Is anyone familiar with using the NI cDAQ 9172?  This is my first time using it and I am not sure what exactly I am doing wrong... Alone with a NI 9233 analog input module, it works great.  I can grab my 4 signals from each channel and go.  However, when I add another analog input module to the mix, it gets an error.  It looks like it is reading only one and not the other.  It bombs at one of the DAQ start task and read task.

Basically, the block diagram is just a double of the one 9233 working alone.  Is there something needed for input to make the 9172 working?  Any ideas?

Any help is much appreciated.  Thanks!!

[Jud~]

In this thread: http://forums.ni.com/ni/board/message?board.id=170&message.id=287948&query.id=87498#M287948, it states that you need to use the two modules in the same NI-DAQmx tasks??  But in another example http://forums.ni.com/ni/board/message?board.id=170&message.id=338289&query.id=87604#M338289, their vi made with the 9172 is made with 2 seperate DAQmx tasks, parallel to each other which is what we are trying to implement.  Is there any simple example available out there for reference as to utlizing the 9172?  Thanks!

[KyleBryson]

Hi Jud,

Both threads are correct.  The cDAQ-9172 has a single analog input timing engine, so both of your analog input modules will need to be in a single task.  The other VI you referenced shows one analog input task (with channels added from two modules) as well as an analog output task.  Analog output has a separate timing engine from analog input, so both of those can run in parallel independent tasks.

The beginning of this thread is a good example; a single DAQmx Create Task followed by a DAQmx Create Virtual Channel for channels from each module.  Also, Getting Started with NI-DAQmx will give you the fundamentals for data acquisition, though I don't know how many of their examples use CompactDAQ.

Regards,
Kyle