• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 32 subscribers
  • Views 1740 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Sensortag CC2650 and HDC1000 humidity sensor drift

Mikael Silvennoinen
Prodigy 40 points
Other Parts Discussed in Thread: HDC1000

I have two CC2650 sensortag's to be used in a cigar humidor monitoring project.

As new I checked the calibration of the Humidity sensor with a Boveda 69%RH humidipak, one of the sensortags showed a steady 69%RH and the other one was a 67.5%RH. Close enough and within spec of the HDC1000 -sensor.

I've had one of the sensortags in a humidor for more than a week now. The humidity seemed to rise a few %. per day which I thought was odd as the analog humidity meter in the humidor was showing a steady 65-70%RH. I took out the sensortag from the humidor when the reading was reaching 78%RH. Strange thing is that it doesn't drop down below 33%RH even after hours in the same space as the other sensortag, which is showing a steady 18%RH. The temp readings are within 0.1 degrees C between the sensortags.

It seems that the humidity sensor starts to drift quite rapidly when operated in humid conditions, what started as a RH difference of 1.5%. between the sensortags is now a 15%. difference in RH.

Has anyone else had similar findings with the HDC1000? Do I possibly have a defect unit?

Cheers,
Mikael

  • 0
    TI__Expert 5145 points

    Hi Mikael,

    As noted in their datasheets, devices HDC1000YPAR, HDC1000YPAT, HDC1008YPAR, HDC1008YPAT, HDC1050DMBR, and HDC1050DMBT may exhibit RH measurement shift. As described in the datasheet section 9.3.2, the RH sensing element goes through a settling process with exposure to time, temperature and humidity. Material before 1527 could settle to an offset of +15%. The typical accuracy (RHACC) range for these devices remains unchanged and not guaranteed. We have recently reduced the potential measurement shift through electrically adjusting these materials and are offering to exchange newer devices (datecode 1527 or after) for older devices (datecode before 1527).

    Probably the sensortags that you are testing mount HDC1000 with date code before then 1527. The datecode is available in the physical marking on the device:

    If this is the case there are 2 possible solutions:

    - Account for RH measurement shift in system performance, or

    - Material (the humidity sensor itself) can be returned to TI for replacement.

    Please let me know your comments.

    Best regards,

    Carmine

  • 0 in reply to Carmine Iascone
    Prodigy 40 points
    Hello Carmine,

    My date code is on both Sensortags 1551.
    If the drift settles down and "stabilises", I could easily account for the offset in my software.

    I'll keep them in a humidity-calibrated environment and monitor the readouts, I'll calculate the offset once I have a steady reading

    Thank you for your quick help!


    Regards,
    Mikael
  • 0 in reply to Mikael Silvennoinen
    Prodigy 10 points
    Hi Mikael, thanks for your post. I bought the Sensortag2 for exactly the same idea to monitor my Cigar Humidor. to calibrate the sensor tag I placed it in a 99% humidity environment and the preloaded TI software that I downloaded from app store read 122% humidity. I haven't programmed in many many years and I can use some help. like to ask whether you can share your code and perhaps help me out. I can be reached at: work at ksaraf dot com. Sincere thanks.