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ADS1131: Reporting erroneous values

user275052
Prodigy 100 points
Part Number: ADS1131

We have been using this part with a load cell in an agricultural outdoor setting.  In some installations, we notice that it provides extreme erroneous data. We may see it drop to zero, and then at another time, report an extreme high value.  It appears that the erroneous data seems to occur at a given temperature (we have a temperature sensor reporting a value on the PCB nearby)  It will seem to occur at a temperature of ~say 85F in one instance.  In another, it will occur at 5F, in  a third at around 40F.  In each of the scenarios, It reports the correct value at all other temperatures.

Any thoughts as to what is occurring here?

Patrick

  • 0
    TI__Guru** 112765 points

    Hi Patrick,

    It would be very difficult to say what might be happening.  The ADS1131 device operating temperature is -40 to 85 deg C, and the temperatures you mentioned are well within that range.

    I would try to discover a commonality to the issue.  Possible concerns relate to load cell connections and excitation, external noise sources, and fluctuating supplies. 

    Does the issue go away on it's own or is some corrective action required to restore proper readings?

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 100 points
    Bob,
    I wish I could send traces... it appears to happen when the outdoor temperature is in a certain range... then readings come in correctly outside of that range.

    1.) Since this is outdoors, humidity/ temperature. I'm wondering if there is a need for con-formal coating with the uv signal changes from bridge.
    2.) we are generating the clock from a PIC micro-controller... it appears that the clock rises in ~ 125ns -ish and we read data 4 us later from the chip

    Any history here?
  • 0 in reply to user275052
    TI__Guru** 112765 points

    Hi Patrick,

    Conformal coating might help, but it is always good to know what is causing the issue before attempting to fix it.  I assume the clock you are referring to is the SCLK, so I don't understand what you are telling me.  Are you saying you hold SCLK high for 4us, and then start the remaining clocks?  What is the SCLK frequency you are using?  Can you give me the rest of the pin settings on the ADS1131 being used?  Do you use the low-side switch?

    It would be really helpful for me to see your schematic and learn more about your system.  You can contact me directly by clicking on my name and then the Connect button to start a private conversation.

    Best regards,

    Bob B