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HDC3022: difference in response time compared to HDC3020?

Stefan Lintner
Expert 4235 points
Part Number: HDC3022
Other Parts Discussed in Thread: HDC3020

Hi team,

a customer would like to know if the PTFE membrane would reduce the real response time, since the water atoms need to penetrate the PTFE membrane first to be detected by the sensor. For example, in case both sensors are exposed to the same change of humidity at the same time, would the HDC3020 react earlier (and thus reach the final humidity faster) than the HDC3022 just because of the protective PTFE membrane?

Do you have by any chance humidity over time graphs that are related to this question?

BR,
Stefan

  • 0
    TI__Guru* 90906 points

    Dear Stefan - 

    Thanks for the post - a water molecule is made from two hydrogen atoms and one oxygen atom. Water vapor is water in gaseous form, and water vapor is what the sensor reacts to. 

    There may be some slight hysteresis between the two variants, but I don't think it would be really noticeable, unless the application was reading the sensors very quickly. 

    Here below is a quick test for you, at my desk, where three of the sensors are HDC3020, one is HDC3022 (pink one), all on same hardware. I am reading these at 100mSec loop interval, and i just breathed on them - click on images to enlarge. 

    First one is with markers before the breath

     

    second one is showing the reaction

    third one shows them meeting, within about 900mSec

    Let us know if you need more information/test examples, etc. 

  • 0 in reply to Josh Wyatt
    TI__Expert 4235 points

    Hi Josh,

    thank you for the the fast response!

    Based on the supplied pictures the response for the 2 different sensors is quite similar in the range between 24 to 27 %RH, although the HDC3020 seems to be slightly faster (only 300 ms time difference to reach the same value).

    Since customers use case would measure humidity between 30 to 100 %RH and they would require a fast response, they would be interested in the resulting graph after a jump from ~30 to ~100 %RH. They assume the time to reach the same plateau will be more distinct now.

    Would it be possible to provide this data?

    BR,
    Stefan

     

  • 0 in reply to Stefan Lintner
    TI__Guru* 90906 points

    Stefan - 

    This was just at my desk, for illustration purposes, with four sensors (three HDC3020 and one HDC3022). 

    With a big step request like that, which would be application specific to them, I would refer them to the datasheet.

    If they truly need us to show them a step response, LMK - that would take a little more time, as it is a little tricky to do that kind of plunge testing.

  • 0 in reply to Josh Wyatt
    TI__Expert 4235 points

    Hi Josh,

    a step response from ~30 to ~100 %RH on HDC3020 and HDC3022 would be very much appreciated.
    This info would help the customer with the decision making.

    BR,
    Stefan

  • 0 in reply to Stefan Lintner
    TI__Guru* 90906 points

    Stefan - 

    I have enlisted some internal resources to gather that direct comparison with a plunge, however - in experimenting with a setup I have here in the office, for the purposes of helping them making a decision between the -20 or -22  - I think I would recommend here if they are interested in speed, the open cavity part will be slightly faster, based on this limited real world testing, then might want to lean towards the HDC3020. This (below) is not a plunge test, but it is with a humidity source (ultrasonic atomizer) being turned on and then some fans controlling the level (being controlled using the thresholds by a fifth HDC302x) - and this is a highly subjective test - the HDC3022 did lag the HDC3022 a bit, but then did catch up - so if they can live with a very slight lag, and they do need the PTFE cover the HDC3022 will work, too. Here I am using a 5mSec loop, so these lag times you will see below are very minimal. If measuring slower, you may not even see them. 

    I will follow up with you when those other captures are available, too. 

  • 0 in reply to Josh Wyatt
    TI__Expert 4235 points

    Hi Josh,

    thank you for this additional input!
    Looking forward to the step response captures.

    Regarding the need of the PTFE filter in customers application:
    In their use case the sensor will be exposed to high humidity levels and might also be subjected to splash water.

    Could HDC3020 deal with those conditions?

    BR,
    Stefan

  • 0 in reply to Stefan Lintner
    TI__Guru* 90906 points

    Stefan - 

    The HDC3022 filter is hydrophobic, it is made for that kind of application need of being exposed to water splashing, as it will shed the water. 

  • +1 in reply to Josh Wyatt
    TI__Guru* 90906 points

    Stefan - 

    The comparison plunge test you requested results showed us that the HDC3022 is a little slower (as we previously discussed) than the HDC3020 on the up-sweep, but still meets what we show in the datasheet as typical response time (typ 4 sec response time over a total range of about 80%RH). The down-sweep indicates no lag between the variants.