Measureing Differential and RSE on USB-6009

[FTIengr]

I'm using  a USB-6009 with Labview 7.1 and the latest DaqMX and DaqMX base. I'm attempting to measure three differential signals on channels AI0, AI1, and AI2. I'm also trying to measure two RSE signals on channels AI3 and AI7. I'm using the DAQ assistant to setup the task. All of the inputs are configured in a single DAQ assistant.

The problem I am having is that it works fine the first time I run the program. But, after stopping and restarting it, at least one of my channels gets switched. Instead of measure the voltage on differential channel AI2, that voltage shows up on channel RSE AI 7. If I completely close labview, unplug the DAQ, wait a second, and then plug it back in and start up my program, eveything works good until I restart the program. I'm completely stumped on this and any help is greatly appreciated.

[devchander]

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But, after stopping and restarting it, at least one of my channels gets switched

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Are you clearing the old task and creating a new task??

[FTIengr]

I don't think so.. I'm not sure what you mean by "clearing the old task".

To be specific, I run the program, then click the stop button, the click the run button again, but I don't touch anything else.

[Mark_E]

Welcome to the discussion forums, FTlengr!

I’ve spent a bit of time acquiring your same hardware and running what I believe to be an equivalent program to replicate the behavior you’re experiencing. I no longer have LabVIEW 7.1 installed on my computer, but I thought I would at least try it on LabVIEW 8.5 first. I don’t experience your issue, so I’m left wondering if it is a difference in program setup or a LabVIEW version change. Please try to make identical code in 7.1 as what I’ve posted in my included screenshot and let me know if you still experience the same thing. If not, check your settings. If you do, send me a screenshot of your setup so I can see why that might be.

By the way, I included the screenshot of the DAQmx VIs as it would take multiple pictures to show the DAQ Assistant settings, but I tried it in both and I don't see the signals switching.

Message Edited by Mark E on 10-11-2007 06:07 PM

[FTIengr]

I was able to fix the problem by not using DAQ assitant, but to instead create the tasks the old way (like you have in the top picture). Thanks all for helping!

I wonder why the assistant had so many problems with this...

[Mark_E]

Hi FTlengr,

I was able to get this to work both with DAQmx as well as the DAQ Assistant as seen by my previous screenshot, so it may have just been a configuration issue in your DAQ Assistant. One way to compare what settings you have versus the DAQmx code that I wrote is to follow these steps:

1. Configure the DAQ Assistant as normal in LabVIEW.

2. Right-click the DAQ Assistant and choose “Generate NI-DAQmx Code”.

3. You will see an untitled subVI that contains the entire configuration. Double-click it and look at the block diagram to see all the inputs and outputs. (One thing to note is that each channel will have its own setup, so it can get rather large. All the differential and RSE channels will have exactly the same parameters except for physical channel names, respectively. My code condensed this to two setup VIs: one for differential and one for RSE.)

4. Compare the generated code’s parameters to those of the DAQmx VIs and see what is different.

I hope this helps you see the similarities between DAQmx and the DAQ Assistant. Feel free to ask more questions if you have any.