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Original question:

ADS1231: ADS1231 Interface

ADS1231: ADS1231 Interface

NAVIN CHAKRAVARTHY K
Prodigy 60 points
Part Number: ADS1231

Hi Bob,

  I have made the corrections that you suggested. Now more fluctuations are happening. Kindly, Help me to get the non fluctuated results.

Thanks & Regards

Navin Chakravarthy

  • 0
    TI__Guru 62905 points

    Hello Navin,

    Bob is out of the office but will return soon.  Would you connect this thread back with the previous one you were working on for reference?  Are the fluctuations correlated in time with any other events in the system - e.g. wifi or other comms transfer?

  • 0 in reply to Collin Wells
    Prodigy 60 points
    Collin Wells said:
    Would you connect this thread back with the previous one you were working on for reference?

    Yes, Collin, I would like to connect this thread back with the previous one

    Collin Wells said:
    Are the fluctuations correlated in time with any other events in the system - e.g. wifi or other comms transfer?

    I have seen the output via Ble. is that the reason?

  • 0 in reply to NAVIN CHAKRAVARTHY K
    TI__Guru 62905 points

    Apologies, but would you confirm the previous thread link?  

    The BLE transactions may be related, but not necessarily.  Let's connect back with what was going on before based on the thread link you'll share and we can provide some insights thereafter. 

  • 0 in reply to Collin Wells
    TI__Guru** 113765 points

    Hi Navin,

    This thread is a continuation of the previous thread:

    https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/1033680/ads1231-ads1231-interface

    In your previous thread you stated that "There is no fluctuation problem with the new setup."  Can you be more specific as to what may have changed now that you are seeing the fluctuations again?  The last set of suggestions were related specifically to code.

    If you are seeing large fluctuations near 0 or a no load condition, then most likely you are not properly sign-extending the 24-bit binary 2's complement value from the ADC to 32-bit signed variable in your code.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 60 points

    Hi Bob,

    Actually, This time is a little different. I have calibrated with a weight of 20.4kg. My setup was the same 4 x 50kg load cell, full scale weight is 200kg. Sensitivity is 1mv/v. Now, I can reach the range of the output. If I put 1000 grams (1Kg means ) it will be fluctuating between 900 and 1150. If I put the weight of 20.4kg it will come to 20,465 but the last two digits are kept on fluctuating.

    is it common or is there any way to control it?

    Regards,

    Navin

  • 0 in reply to NAVIN CHAKRAVARTHY K
    TI__Guru** 113765 points

    Hi Navin,

    You have not stated the SPEED setting used on the ADS1231.  Using the Analog Engineers Calculator I mentioned in the previous thread it is not possible to achieve a steady result even at 10sps.

    As you can see here, 20 scale counts is about the best you can do with respect to the ADS1231.  It will be even worse at 80sps.  If there is additional noise pickup on the wiring, then this will add more code fluctuation.  So if you are seeing 100-150 codes of variation, then you are most likely picking up some additional noise.

    What I would suggest at this point is for you to get to the performance level as shown in the diagram above by connecting a voltage divider (using two 10k resistors) connected in series from the excitation source to ground.  At the junction of the 2 resistors, connect to both AINP and AINN of the ADS1231 to act as a short.  This will make sure that the input is within the proper input range and should hold a more valid result.  With this configuration you should not see more than 20 grams of variation.  If you do then you have something wrong with your setup and can be related to the supply or grounding.

    Once you have verified the ADS1231 performance, you can go back to the load cell setup and try to determine the source of the noise and how it can be effectively treated.

    Best regards,

    Bob B