Wet RuuviTag

I have a RuuviTag on my porch, that is, outside. It reports 100 % humidity, and I wonder if this can be correct. I am not so familiar with meteorology but so much 100 % sounds odd.

The RuuviTag is not underwater for those who may wonder. The only unorthodox thing about the RuuviTag is some sticky tape in front of the white membrane on the plastic cover, to keep birds from pecking a hole there (happened once, maybe they think there is food inside the case).


If the sticky tape blocks the breathing membrane the moisture inside has no way to escape, and condensation will form inside the tag and sensor element. That gets reported as 100% moisture.

We have X-rayed and analyzed a few sensors that report obviously incorrect readings, usually there are some contaminants inside the sensing element. For example it’s possible that humidity has condensed inside the sensor and left minerals (salt etc) in the element after evaporation. The contamination causes sensor to report incorrect readings.

When I looked inside, it did not look wet (no droplets) but I guess 100 % humidity does not require droplets. I will try to figure out a better way to protect the sensor from preying birds.

Anyways, I assume it is not common to have such long and repeated periods of 100 % humidity outside, and the reason must be my sticky tape covering the membrane. I hope I have not damaged the sensors inside.

I am currently tracking one regular Tag and one ProTag outside my house. They do not show the same temperature reading and do not react equally fast to changes but that is probably because the ProTag is on the outside wall, with some temperature inertia from the house, and the other at the corner of the roof, directly exposed to winds and not affected by the walls.

Or would the 2-in-1 ProTag be slower to react to temperature changes than 4-in-1 regular Tag, due to better sealing and thicker case?

RuuviTag Pro reacts a bit slower due to thermal mass of enclosure. Here’s a plot of response times we made a short while ago.

Thanks for the plot. I assume BME and SHTC are both the regular RuuviTag but different sensors, and Pro external is Pro but with an external sensor, i.e., with very little mass and warming up quickly.

I try to plot my two outdoor sensors, Pro on the wall and regular Tag under the roof. In my case, however, I assume the smoother curve of the Pro is at least partly due to being on the wall.

Although this is mostly directed at the BME280 it might be of some help
Ruuvi Wiki Temperature & Humidity