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HDC1080: Unstable Readings

Alan McCormick
Prodigy 20 points
Part Number: HDC1080

We are currently testing a HDC1080 chip as a replacement for an atmega2560 based learning project kit.

The readings appear to be unstable on our test chip with a >10% variance between readings:

T=33.97C, RH=38.59%
T=32.88C, RH=38.68%
T=34.95C, RH=38.81%
T=33.60C, RH=39.12%

(1000ms between readings)

((float)temperatureR)*165/65536 - 40; // (TempRaw/2^16)*165 - 40

((float)humidityR )*100/65536; //(HumidityRaw/2^16)*100

(resolution to 14 bits)

  • 0
    TI__Expert 5695 points
    Hi Alan,
    Let me ask you some questions to understand what is going on, since the temperature measurements you are sharing is fluctuating around +/-1C and this is not the expected behavior on the device , since we expect a max error on temp of +/-0.4C.

    Are you using the HDC1080 EVM to run this measurements?
    Is this experiment in a controlled environment (temp chamber) or using a temperature reference probe to compare with? Any AC, fan or air flowing close to the IC?

    Regards,
    Jose
  • 0 in reply to Jose Arteaga4
    Prodigy 20 points
    Good evening Jose,

    No, this is a commercial break out board (ClosedCube) connected to and coded via the Arduino IDE (the board uses an atmega2560).

    It's currently being tested in the office, minimal air movement and stable air temperature. We have several other sensors in testing (Bosh BMP280, and Silicon Labs Si7021) which show stable temperature and humidity so I do not think it is an environmental issue - however I can request access to the chamber.

    Do you think it may be a problem with the device? I can ask for another sample to exclude failure.

    Thanks
    Alan
  • 0 in reply to Alan McCormick
    TI__Expert 5695 points
    Hi Alan,
    I think is a good idea to get and try different parts, since the reported behavior is not the expected one.