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HDC1080: precision of Temperature and Humidity

PRASANTH V
Prodigy 30 points
Part Number: HDC1080

Hi 

We made out custom design  with TI HDC1080 for Measuring Temperature and Humidity , For  Testing we kept around 15 sensors in same place , why all the sensors gave different reading (small variation is acceptable ) but humidity vise i am seeing Huge variation among sensors (10 - 12% ), Why ?? 

How can i calibrate these sensors ?

  • 0
    TI__Expert 5695 points
    TI support team will contact you shortly.
  • 0
    TI__Genius 13650 points
    Hello Prasanth,
    what is the spread of the temperature readings that you see between the different sensors? Since RH% readings take temperature into account, we should first find out if the issue on your board is caused by a temperature measurement error or a humidity measurement error.
  • 0 in reply to Ben Kasemsadeh
    Prodigy 30 points

    Hi 

    Thank you for your reply..

    i am seeing 0.5 - 2  degree variation among all the devices...

    thank you

  • 0 in reply to PRASANTH V
    TI__Genius 13650 points

    Hello Prasanth,

    2 degree temperature variation is actually quite a lot. For each 1 degree temperature variation, %RH changes by 5%. For example, increasing temperature from 25C to 26C at 50%RH would change the %RH reading by -2.5% (5% of 50%RH). 

    Is it possible that HDC devices are influenced by other heat sources on your PCB such as power management ICs or processors? PCBs need to be laid out to minimize heat transfer from nearby components through the PCB itself. This apps note was written for temperature sensors, but the same layout techniques (isolation island etc)  apply to humidity sensors: http://www.ti.com/lit/an/snoa967/snoa967.pdf . 

  • 0 in reply to Ben Kasemsadeh
    Prodigy 30 points
    Hi Ben
    Thank you for your reply..

    Edge Connector
    A miniature PCB that contains only the temperature sensor and is mounted using an edge connector to
    the main PCB is a highly effective method for avoiding significant heat transfer from the main PCB to the
    temperature sensor. The edge connector should ideally be mounted at a location away from major heat
    sources on the main PCB so that radiated heat from ICs does not interfere with the temperature reading.

    i am using Edge connector - set up , Sensor PCB kept away from Main PCB(Sensor PCB <=> Main PCB connected via BUS length of 8cm)

    Thank you