Humidity value reacts slowly to changes, averaging used?

Greetings from a new RuuviTag user. :slight_smile: I noticed that all my four RuuviTags (using latest firmware v3.31.1) react quite slowly to humidity changes, compared to my two cheap digital humidity meters I bought from Clas Ohlson. For example, when I open balcony door, or turn on the shower, my cheap meters react almost instantly (3-5 minutes), but for RuuviTag it takes about 30 minutes to reach new min/max level.

I assume some kind of filtering / averaging of the humidity values is used, to reduce the noise. What kind of filter is used, if any? Where can I find this filtering in firmware source codes?

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The slowness is mainly caused by the gore-tex sticker in RuuviTag enclosure, it has some delay in letting moisture through. RuuviTags up to hardware variant B6 have enabled internal low-pass filtering of BME280 sensor, tags made in last 2 years or so have SHTC3 sensor which does not have such a filter.

The code is available at GitHub - ruuvi/ruuvi.firmware.c: Ruuvi Firmware version 3. Built on top of Nordic SDK 15, uses both Ruuvi and external repositories as submodules. In Beta, no breaking changes are intended but may be done if absolutely necessary and the lines to disable BME280 filtering would be
-> (1U)

You can remove Goretex-membrane when you are using sensors indoors and place the round hole on top of the sensor (~3mm left from the golden battery connector). This will speed up the changes.


Thanks for your responses. So, basically, there is a Goretex sticker -based “mechanical filter” in RuuviTag. The slowness is not a problem for me, I was just curious. :slight_smile: Actually it is a good thing, since it filters out some measurement noise, although I don’t know how noisy the sensor values are without any kind of filtering. And because of this “filtering”, I can use smaller hysteresis if I want to control my Ufox humidifiers with RuuviTag and smart power outlets.

BTW, does the alignment of the hole in relation to sensor matter, when the Goretex-membrane is used? And when the products are shipped, is the hole always aligned with the sensor?

^ How about the alignment of the hole, @otso & @henri ?

Based on the tests it’s a bit faster if you align to the top of sensor (black sensor with hole in the middle, located ~3mm clockwise from the golden battery clip).

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@henri Is the hole aligned with the sensor before the products are shipped?

Typically yes, but users can turn them however they like. But it has also very small impact to measurement.

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