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HDC1080: Influence of pcb-temperature on humidity measurement

Matze
Prodigy 191 points
Part Number: HDC1080
Other Parts Discussed in Thread: HDC2080,

Dear supporters,

I use your HDC1018 Humidity Temperature Sensor on a PCB for a gas sensing application.

Due to design limitations the sensor is not good enough thermally insulated from the rest of the PCB so that the temperature measurement is always 2 °C above ambient air temperature.

Does this temperature increase influence the humidity measurement?

Is the humidity sensor a capacitive humidity sensor?

Does the humidity sensor internally measure the absolute humidity and calculate the relative humidity with the temperature data or does it directly measure the relative humidity?

How can I compensate the humidity deviation (if it is influenced by the temperature measurement deviation) without changing my PCB design?

Thanks a lot in advance.

M.Hein

  • 0
    TI__Guru* 91086 points

    Dear M.Hein - 

    Yes the %RH sensor system is capacitance measurement based and also yes, the humidity measurement value returned is generally inversely proportional to the temperature offset - for example, if temp error is present, then it will affect the %RH by reporting it lower than actual. You can either characterize the offset and apply math after the measurements are returned or move to the HDC2080 and use offset registers with values derived from your system characterization. 

  • 0 in reply to Josh Wyatt
    Prodigy 191 points

    Thank you!

    Are there any recommended math operations for compensating temperature-offset-error influence on humidity measurement that you can provide to me?

    Is the HDC2080 pin compatible to HDC1080?

    BR

    Matthias

  • 0 in reply to Matze
    TI__Guru* 91086 points

    Matthias - 

    yes the HDC2080 pinout lines up with HDC1080 pinout, so you can directly move. You do need to update your I2C commands / handling  - the HDC2080 does have a different register map. 

    The level by which you can adjust the %RH with the offset registers is such that the complexity of the math would vary with how precise and accurate your applications requirements demand and what kind of volume you are trying to produce. General concept is that you would characterize lots or individual units and apply a general or specific offset based on averages or points along the range.