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HDC1000: stuck on 99.99 relative humidity

Bnaya Hami
Prodigy 10 points
Part Number: HDC1000
Other Parts Discussed in Thread: CC2650STK, HDC3022, HDC2022

Hi
I am using CC2650stk SensorTag. as part of my reaserch I am trying to use the sensor to measure relative humidity and temperature in the soil (for agricultural reaserch)
I desgined and printed a modular and (passivly) ventilated case to allow airflow through the sensor. It's hard to explain exactly what I did, so I attached a picture to make things more clear. the case placed inside the soil so the upper part protruding above the ground, the sensor itself isn't touching the soil (between the parts there is a grid that prevent it)

anyway, the sensor keeps showing 99.99 relative humidity, even when the soil is dry. To the best of my knowledge, there was not condensation on the sensor.

Do you know what may be cause for this issue? Is it necessary for a reliable measurement that there will be air movement around the sensor all the time?

I hope it's clear enough 

Thanks in advance

Bnaya


  • 0
    TI__Guru* 91086 points

    Dear Bnaya - 

    The HDC devices are not made to measure soil moisture - they are made for measuring water vapor present in the air. In this case, I would recommend that you take the PCB out of the enclosure, inspect it under a microscope to see if there are any indicators that water or other material is trapped and dry it out if necessary (if possible using 100C oven for at least an hour, possibly more) , then retest to see if the water has been evaporated from the part. I would also recommend that you might want to use a device with a PTFE filter installed on the part, i.e. HDC3022 or HDC2022, for this application experiment, as they might be better suited for this type of application vs. completely open cavity sensor.