Calibrating multiple strain gages

[j_g@crl]

Hi All,

I'm having trouble getting accurate readings on a strain acquisition setup. I have (9) gages linked to (2) NI 9237 strain gage modules, which work fine until I want to zero out the readings by clicking "Remove Initial Voltage". The program freezes for a moment before crashing.

I know the gages and the software are working properly, as I've been able to open separate projects for each module, zero each gage individually, and collect data using 2 projects. Having all the gages on the same project also works until I click "Remove Initial Voltage". 

My question is if it is possible to calibrate and run all (9) gages on the same project? Or is there a limit to how many readings each project can handle?

Thanks!

-JG

[cdaug]

Hey JG,

What version of DAQExpress do you have installed? The newest version available now would be DAQExpress 3.1 with NI-DAQmx 18.6.

Would you be able to share the DAQExpress project you've been using for this project on the forum? I'm going to take a look at some of the shipping examples to see if any of those replicate.

If this is unexpected behavior, the goal for us would be to file a Corrective Action Request on your behalf with our R&D department. We will need more information before we get to that point, but that's likely a future step once we get a good amount of clarifying information!

Best,

Chris D. | Applications Engineer | National Instruments

[j_g@crl]

Thanks for your reply, Chris.

I'm currently running DAQExpress v1.0 with NI-DAQmx 17.1.

For some reason, this messaging system does not allow me to attach .lvproject or .task files to this reply. 

You might have to manually set up the project with the parameters below:

Signal Type: Strain Gage

Bridge Type: Quarter I

Excitation: 2.5V internal

Gage Factor: 2.135

Resistance: 350 ohms

Adding more than 4 inputs into one task and attempting to calibrate any input would result in a crash.

The solution I have been working with is splitting the task into two separate tasks with 4 inputs per task. If it would be possible to run all gages under the same task, that would be optimal.

Look forward to hearing from you,

-JG

[cdaug]

Hi JG,

I couldn't reproduce the behavior in the newest version of DAQExpress (3.1.0) with DAQmx 18.6. I would recommend upgrading if possible. You should be able to do this in NI Package Manager pretty easily.

I did the following to reproduce the project, I attached a ZIP file of my DAQExpress project and task.

1. Created a new DAQExpress Project
2. From the SystemDesigner tab (may not be an option in older versions of DAQExpress), I selected my first 9237 and selected Create Analog Input.
3. I set up a single channel with the parameters you included in your last post.
4. I used the button Duplicate Input to create 7 more copies for a total of 8 channels across 2x 9237 modules.
5. I used the Remove Initial Voltage checkbox and everything worked as expected.

Let me know if you run into any other issues after upgrading!

Best,

Chris D. | Applications Engineer | National Instruments