Shelly HT erroneous readings

    Hello

    I have several (8ea) Shelly HT that I've setup and done some testing prior to installation that were bought recently and updated to latest firmware (20210413-154417/v1.10.2)

    First I put the Shelly HT's inside middle of a small room. For comparsion I've added other humidity and temp sensors, both analog hygrometer and digitals (Aqara's, NEXA).

    The temp readings of all sensors were within 0.5C so its more than good. But the Shelly HT's humidity readings in differed from 40% to 69% while the rest of the other sensors were in the range 54-57%

    This lead up to testing the sensors in a sealed controlled enviroment like you do with cigar humidor cabinets hygrometers.

    The test conducted have been performed in a plastic sealed container in two test rounds for ~24hrs each. First round in a 75% humidity / 23C and next 100% humidity/ 23C.

    First round (75% humidity reference) the Shelly HT's were between 80-100% (1ea at 80%, 4ea @ 100% and the rest around 90%) while the other sensors showed between 71% (Nexa) and 74% Aqara's (2ea) / Analog (1ea).

    Round two (100% reference) all Shelly showed 100%, as suspected! The NEXA showed 87%, Aqara's 97% and Analog 100%

    This seems good but makes the Shelly OFFSET function unusable as you cannot calibrate the offset difference and still make it show "more" correct readings in the full 0-100% scale.

    I have tried contact Shelly support and also create a ticket but still have got no replay regarding the humidity sensor drifting and if its considred normal this large and unconsistent offset. Of course its no precision sensor but the large fluctuations bewteen the HT's readings makes the humidity function kinda useless I think.


    Anyone else here at the forum have similar experience regarding erroneous readings of the Shelly HT?

    Yes I have similar results with mine. The temperature is accurate when compared to other sensors I have, but the humidity is way out. When the average of a bunch of other sensors (and the reported weather service humidity) is around 45%, the Shelly H&T is reporting 69% !

    In addition to the inaccuracy, you can see in the attached chart it's very slow to react to changes. This shows it placed in the bathroom right next to an aqara zigbee sensor, and the spikes are two seperate uses of the shower. This is my primary use for this sensor - turning on the fan when the humidity spikes from the shower and off when it returns to normal. You can see in the chart how slowly it both rises AND falls compared to the aqara.

    I currently have an offset entered of "-24" which at some levels makes it correct, but as you can see in the chart, and as tested above by libreiot, the innacuracy is much less when closer to 100% and the offset would make it vastly underreport at this level.

    I've relegated my H&T to a task that requires less precision, and am only using Zigbee sensors now (I've been really impressed by the Aqara ones). Still love my Shelly relays & dimmers, but IMHO all the battery based products suck (this is as much a weakness of WiFi than the Shelly implementation itself)

    Fully agree. I have 2 H&T and they are both showing rubbish. In my setting both say >85% humidity, but all other 3rd party sensors show <70%. If there would really be >85% in my rooms I am sure I would feel it when sleeping and living there in these rooms....

    11x Shelly1 (V.3) an 12V +3x Temp-AddOn, 1x DHT22 Add-On, 2x Shelly1 PM an 230V, 9x Shelly Flood, 2x Shelly D&W2, 1x Shelly EM, 1x Plug S, 1x Plug, 4x H&T, 1x Motion1, 1xButton

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