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HDC1010: Sensor accuracy - out of the box, and over time.

Jim Wiese
Prodigy 30 points
Part Number: HDC1010
Other Parts Discussed in Thread: HDC2010, HDC2080

Does the accuracy of this temp/hum sensor deteriorate over time?   Out of the box the accuracy is RH +-2% and DB +-0.2. I use this sensor in my controls and have found the accuracy as stated in the specs.  My problem is the HVAC industry has a study that recommends not using differential enthalpy control for economizers because the sensor accuracy is reported at RH +-5% and DB +- 2 degrees.     I want to try to revise the building code but want to make sure that there is not a calibration issue over the service life that would cause a significant accuracy error.  Thank you. 

  • 0
    TI__Guru* 91146 points

    Dear Jim - 

    All polymer based humidity sensors will drift some over the long term. This can be accelerated by simultaneous high heat and humidity conditions. The HDC1010 has been characterized to have ~+/-0.25%RH/year drift under indoor environmental conditions. This of course means after 10 years, for example, you could see up to 2.5%RH drift as a result of the aging. 

    This parameter is listed in the datasheet on page 5 http://www.ti.com/lit/ds/symlink/hdc1010.pdf as RHLTD

    Also, is there a reason you chose the HDC1010 specifically over the HDC2010 or HDC2080?  

  • 0 in reply to Josh Wyatt
    Prodigy 30 points

    Josh,

    Do you know if the drift is consistently in the same direction and the same amount or is it random. I have an indoor and an outdoor sensor that are subject to about the same environmental factors.  Will they both drift in the same direction so that the differential is not as distorted?  Or is it +/- .25 so the difference between the 2 could be 5rh if the drift is in opposite directions. 

    Thanks

  • 0 in reply to Jim Wiese
    TI__Guru* 91146 points

    Jim - 

    in the stress condition testing results I have seen they all drift in positive direction - however I will ask our testing and development folks to make sure this is always the case.

  • 0 in reply to Josh Wyatt
    Prodigy 30 points

    Josh,

    When you say they drift in a positive direction does that mean an increase value?  If they drift in the same manner the absolute difference between 2 sensor of the same age should be a fraction of the drift.  Is this a good assumption?  If so the issue of sensor accuracy should not be a limiting factor in differential humidity or enthalpy controls.  Make sense? 

    Jim

  • 0 in reply to Jim Wiese
    TI__Guru* 91146 points

    Jim - 

    we do have +/- on the characteristic - and this value may be impacted by dust, vaporized solvents, outgassing of tapes, adhesives, packaging materials, etc.