Dear sirs! I'm in process of selecting humidity monitoring solution. The main contender is TH10 + Sonoff Si7021 Sensor. However, before placing orders I want to know some detail of sensor inner working.
Accordingly to SliliconLabs Si7021 sensor datasheet: "If the Si70xx is used at the dew point and condensation occurs on the sensor, the on-chip heater can be activated to dry the sensor and restore operation once the sensor is above the dew point."
The Sonoff Si7021 sensor planned to be used in place where RHS can be over 80% by times and the problem with dew point and condensation will definitely in place.
So there is my question: do the Sonoff system consisting of TH10+Si7021 uses internal heater to make sensor reading correct after RHS becomes greater than 80%?
I am also using Sonoff Si7021 Sensor heater and its really working well, I bought it last month from Arts and supplies coupon codes at ReeCoupons, it will definitely correct your sensor reading, you will not face any issue after fixing it.
Thank you for reply. However, I think you misunderstood my question. I'm asking not about controlling heater with sonoff, but about very small heater EMBEDDED into sensor which should be controlled by Sonoff TH module. In a high humidity environment (> 80% RHS), the sonoff TH module must periodically turn it on and off to raise the temperature of the sensor and cause it to dry out to obtain a correct humidity reading. If it does not control the sensor heater, the maximum humidity range available for measurement is 80%. This is sufficient for an arid, but not sufficient for a humid area.
Btw, sonoff site only adds vagueness about sensor capabilities. Citing "https://sonoff.tech/product/accessories/si7021": from "Wider Measuring Range" section sensor's humidity range is "0 to 80% RH". But "Specifications" section declares "Humidity Measuring Range: 0 ~ 100%RH".
So what is the truth? 80% or 100%? Do Sonoff TH module use sensor embedded heater or not?
Seems Sonoff tech support is not much of good - the ticket with the same question is being processed above the week already.
Hi John, I was looking to buy the Sonoff Si7021 as well with some online coupons and I was searching for more information about it and I stumbled upon your post. Did you find out how the heater is configured? I am interested in this too.
Hi! Unfortunately, no new information on this topic is known. Sonoff ticket with question is still being processed. However, all the facts known so far indicate that if your environment can exceed 80% RHS - you better search for an alternative solution than Sonoff TH + Si7021 sensor.
If you is ready for little tinkering - there is great Bosch BME280 sensor in the wild. An alternative physical principle is used to measure humidity, so an internal heater is not required. Guaranteed measurable humidity range from 0 to 100%. Unfortunately it is not available as an official Sonoff product and is not supported by official firmware. However it can be connect to Sonoff TH (or ever Sonoff base!) module with alternate firmware, such as Tasmota. Internet full of information for performing such mods.
As a side note - how ironical that the moderation process, which delays posted messages for several days in fact stop very little spam if stop any at all. Thank you good moderators for making [near-] realtime communication impossible :-)
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