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HDC1080: Heater

Mohammadreza Zonnar
Prodigy 10 points
Part Number: HDC1080

In one of the posts it’s mentioned that HDC1080 is able to auto detect the condensation. Is there any flag, or register for that? Or we need to check RH to see
if it drops from 100% to 0 or not. So if we should check it all the time is not auto detected anymore.
The next question is, as I found we set the heater flag and after that in each measurement request the heater gets ON and off until the next request and,
if we want to increase ethe temp faster we have to read the sensor faster? Am I right?
In the other word, what’s the duty cycle of being ON for heater ?
And based on the post we should keep the flag enable until we see the jump from 0 to 100%? How the RH value looks like before it happen?
I mean, for example the RH was around 100% and then jump down to zero, the we turn the heater on, and then RH start to decrease gradually and when it’s close to
zero it jumps to 100% and we need to turn it off then?

  • 0
    TI__Genius 11955 points

    Hello Mohammadreza,

    Let me answer your questions one at a time.

    1) I believe this is the post you are refering to about the "auto-detect": HDC1080 Heater auto-detect. There is no register, flag, or alert pin that will tell you when condensation has formed on the sensor. The RH will need to be checked to see if it drops from 100% to 0%. The post presumes that a user will be continuously measuring RH from the HDC1080, so capturing a 100% to 0% drop would be the flag to look for. But if a user is not continuously reading from HDC1080, then they would need to trigger a read to see if it reads 0%. So you are correct that in that instance where a user wasnt going to continuously read RH anyway, it isnt auto-detected anymore.

    2) The heater is ON only during the conversion time. It means that the temperature increase is related to the output sampling frequency. So for duty cycle, I would measure the HDC1080 at least once per second until the condensation is removed or the desired temp rise is achieved.

    3) If you are running the heater to remove condensation, the humidity shouldn't steadily drop as the temp rises, it should stay at 0% until the water droplet is boiled off which will trigger a spike back to 100%. If there is no condensation, then the humidity will steadily drop as the heater temp increases.

    Regards 

    -Alex Thompson

  • 0 in reply to Alex Thompson
    Prodigy 10 points

    Hello Alex and Thanks for your helpful answers which address almost all my questions. I fully understood how it's working but it brings me another question.
    Based on what you said, when I am running the heater to remove the condensation the humidity is still 0% until droplet is boiled off completely after that( in next measurement)  I would see a jump from 0% to 100%, which acknowledges me to turn off the heater because no need to keep it on anymore. 
    Q) After seeing jump from 0 to 100%, what will I read in next RH measurement ?( is it possible to Rh is still showing 100% or it's just happens once?) The humidity value starts decreasing gradually from 100% to real current value? or jumps to the real value ? 

  • +1 in reply to Mohammadreza Zonnar
    TI__Genius 11955 points

    Hi Mohammadreza,

    If you are still running the heater after the water droplet has evaporated, then you should see RH decrease quickly to a very low RH (possibly 0%) because as the device temperature increases RH readings will decrease. If you are only running the heater until the water droplet is removed and stopping it (so it goes from 0% to 100%), the humidity value should gradually decrease from 100% to the real current RH value, it shouldn't immediately jump to the current value. If the HDC1080 is still reading 100% after the condensation is removed, the ambient RH could be 100% in which case it is sensing correctly, or you can try briefly running the heater again to lower the device RH readings to push the HDC1080 to return to the true current RH value.

    Regards

    -Alex Thompson