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ADS1120: Temperature sensor value error

Kartik V63
Prodigy 30 points
Part Number: ADS1120

I have ADS1120 configured to measure the internal temperature from the sensor in the chip. There are no external hot objects near the sensor. So technically its should read room temperature (this is what I think). The room temperature is about 22-23C but the sensor reads 30C. I did shift the register value (right shift 2 bits)  and multiply the decimal value by 0.03125 as mentioned in the manual still it reads 30C. Can anybody know any reason for this?

Config registers:

Reg 0 : 0000 0000

Reg 1 : 0000 0110

Reg 2: 0001 0000

Reg 3: 0000 0000

Thanks,

Regards,

Kartik

  • 0
    TI__Guru** 113765 points
    Hi Kartik,

    Welcome to the E2E forum! Thanks for sending the configuration settings. As you are using continuous conversions, are you reading the conversion results directly or by using the RDATA command? It also would be helpful to see several raw ADC results before calculations to determine if there is some other issue.

    The ADS1120 temperature sensor does not monitor ambient temperature, but rather the silicon die temperature within the package. If surrounding components or PCB is warmer than the ambient room temperature you will see a difference. Also, there may be a small amount of self-heating, but this would be a very small variation for the configuration you are using. A 7 deg C difference from ambient is significant, so check the temperature of any thing around or near the device that may be generating heat.

    Also check to make sure there isn't an error when reading the result from the device. The 30 deg C reading is result data from the ADS1120 of 0xFF00. This temperature should fluctuate some. I would try applying heat or cooling to the ADS1120 to see if this value fluctuates to make sure you are reading and calculating the result properly.

    Best regards,
    Bob B
  • 0 in reply to Bob Benjamin
    Prodigy 30 points
    Hi Bob,
    Thanks for the suggestion. I did actually check the value and it is fluctuating (according to the last part of your reply). I was assuming that the temp sensor responds to the ambient temperature. I will check to see for any other heating points near the sensor.
    To answer your first question, yes I am directly reading the results (since I don't have to send START/SYNC every time as in single-shot mode, I only send it once).
    Thank you for your assistance.

    Kind regards,
    Kartik