ni9237 excitation voltage

[gregl]

Our cRIO module NI-9237 Strain gage analog input module is not reading anything from a couple different load cells.  I am not getting any error messages, but suspect the h/w.  when i set the excitation voltages without anything hooked up I expected to see this value between EX- and EX+.  If i do not get anything is it correct to say that it is a hardware problem with the NI-9237 module?

Thanks for the help.

[Jordan_D]

Hi gregl,

A lack of excitation would certainly result in the behavior that you're describing. One possible reason for the lack of excitation could be that your 9237 is configured for external excitation. Another possible reason could be that you have not yet started the task. I would recommend creating a task in MAX and before taking any measurements over the EX+ and EX- make sure that you have saved and started the task. Keep me posted on the results.

[gregl]

Jordan,

I am not sure how to create a task in MAX but I did simplfy my code and will try and attach it to this message.  I believe that I do corectly start and stop the module.

[gregl]

I also wanted to add that I connected up the load cell to a cFP-140 strain gauge module and it worked OK...

[Daniel_E]

I would recommend trying the shipping example for the 9237 called "NI 9237 Getting Started" by going Toolkits and Modules >> FPGA >> Compact RIO >> Module Specific >> Analog Input in the Example Finder.  It may be that you are starting and configuring the modules at the same time.  In the example, they have a structure that does configuration and then has another structure to start.  Also, make sure to check for errors.

Also, have you tried other slots?  Do you have another 9237 to try out?

Let us know how this goes!  

Thanks!

Dan

[gregl]

I changed my program to set the parameters first than to start the module and I am now getting the expected excitation voltage measurements on the load cell end of the cable.  However, I am not getting AI readings back.  I have used both of our 9237 modules and have the same problem.  I have tripple checked the cable and it looks ok.  I do sometimes get a "network error" when i try and run the program that says the following:

Target Specific Error Encountered

A driver for the target returned the following error.

Error Code: -63040

NI-RIO FPGA Communications Framework: (Hex 0xFFFF09C0) A connection could not be established to the specified remote device.  Ensure the device is on and accessible via the network, and that it is listening on the correct port.

I am connected directly with a switchover cable so there is no other network traffic.  Also as a bit of history, we originally had a cRIO-9004 controller and we recently upgraded to a cRIO-9012.  I was told that this was just a simple H/W switch only.  Could there be some sort of a communication problem?

[Daniel_E]

Depends.  You will need to update your project to reflect this.  Did you also update the IP in MAX, your project, ect?  Also, when you say you are not getting any AI readings back, do you mean you don't read anything?  Or do you read zero?  Also, are you measuring the voltage going into the card?  Is it different then what the card is reading?  How are you passing back the data to the controller?  Are you calibrating the data to a double on the RT host?  If so, how are you doing this?

Let me know!

Dan

[gregl]

Well it now works again...

It looks like there were a number of issuses.  First, the controller was not set up correctly.  The IP address was set to a conflicting location and the DNS was set incorrectly.  Secondly, I had not changed the controller in this project to reflect the new 9012 model.  Third, the drivers on the 9012 controller are newer than the host PC's (still working to correct this, I have the local support staff helping me).  And forth, the cable did have an error in its design too.  So other than that it was all hunky dory.

Thanks for your help!!!!

[Daniel_E]

LOL.  No problem!!  I am glad it is working!!