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PGA309 temperature calibration

Sudheer Beligere
Intellectual 270 points
Other Parts Discussed in Thread: PGA309, OPA2188

I am using PGA309 with a sensor in output voltage mode, need to do multi point temperature calibration. since i am using 0-10V outtput with a sensor (PGA+ output buffer) I will not be able to use the EVM software for this temperature calibration. 

is there any  document that helps with calibration flow and also computing calibration coefficients? 

I understand from documents that the temp comp of zero and Span are done through piece wise linear interpolation. it would be helpful if any such documents are shared to help me do this multi point temp calibration

thanks and regards,

Sudheer

  • 0
    TI__Genius 17737 points

    Sudheer,

    I believe that the EVM can be used to calibrate 0V to 10V devices. In order to do this you will need to use the external 34401A DMM. The built in A/D converter will be damaged if more than 5V is applied to it. The “Change DMM Interface Emulator” button on the “Set up Cal” tab can be used to select the 34401A DMM. You can communicate with the DMM using an NI-488-HS card or a serial port. In addition to using the 34401A DMM, you will have to change the Pre-cal file to set the output voltage range to 0V to 10V.

    I am going to set up the hardware in our lab to confirm. This will take some time as I have to build a level translation circuit to connect to the PGA309 output. I will post more details once I have confirmed this in lab. If you have an 34401A DMM, you can try it as well.

    Best regards,

    Art Kay

  • 0 in reply to Art Kay
    Intellectual 270 points
    Hello Art,
    thanks a lot for your reply and also glad to know that we can do 0-10V calibration by tweaking the EVM. look forward for your suggestion and steps if you have tested this already.
    Thanks and regards,
    Sudheer
  • 0 in reply to Sudheer Beligere
    TI__Genius 17737 points

    Sorry for the delay on this; I'm on a short busness trip.  I'll be back at the lab on Monday and I'll confirm that this works and document my results.

    Thanks,

    Art

  • 0 in reply to Art Kay
    TI__Genius 17737 points

    I just tested the EVM + output amplifier (0V to 10V output range) today.  Unfortunately, the software will need modifications to accommodate this function. I’ll make the change and post the modified software. Sorry for the delay.

    Best regards,

    Art

  • 0 in reply to Art Kay
    TI__Mastermind 27715 points

    Hello Sudheer,

    Art has made the necessary modifications to the software, and I have tested and verified its functionality. Please download the software at the link below. Let me know if you have any issues accessing the file.

    https://txn.box.com/s/51pk4x13iw5wlz9znl1pe40wqiz2gzp6

    In order to enable the new functionality, do the following steps:

    • Navigate to the "Create Pre-Cal File" window
    • Enable "Secondary Output Stage" in the bottom-left
      • Enter the ideal gain (in V/V) and offset (in V) of your output scaling circuit
    • Enter the total module output high and low target in Step 10
    • Save the pre-cal file and use it as before.

    In order to achieve 0-10V output with the 0.5-4.5V output available from the PGA309, I used a simple gain/offset shift circuit using the OPA2188 with a gain of 2.5 and offset of -1.25V as shown below. This gave me excellent accuracy results after calibration.

    For now, consider this a beta version. There may be bugs we have not yet addressed. We will make some additional improvements to the software and release a new version to the TI Web in the coming months.

    Best regards,

    Ian Williams
    Linear Applications Engineer
    Precision Analog - Op Amps

  • 0 in reply to Ian Williams
    Intellectual 270 points
    Hello Ian, thanks a lot. I amo not able to access the link that you sent, please do provide the access.
    Thanks and regards,Sudheer
  • 0 in reply to Sudheer Beligere
    TI__Mastermind 27715 points

    Hello Sudheer,

    Here is the direct link: txn.box.com/.../51pk4x13iw5wlz9znl1pe40wqiz2gzp6.zip

    Best regards,

    Ian Williams

  • 0 in reply to Ian Williams
    Intellectual 270 points
    Hello Ian,
    I am not able to access the link, i did try this in different browsers but with no success. Not sure what the issue can be?
    does this need any software installation?thanks and regards,Sudheer
  • 0 in reply to Sudheer Beligere
    TI__Mastermind 27715 points

    Hello Sudheer,

    I'm not sure why you're not able to access the link, as permissions were set to open.

    Let's try a different file host. Please try this link: 

    Best regards,

    Ian Williams