Humidity stuck on 100%

I’ve had three Ruuvitags for a few years now.
One that is outside in a porch area out of the rain has been showing 100% humidity regularly recently.
I have just noticed that this 100% persists even when moved back indoors beside one of the other sensors i.e. the environment is not 100%.

Is there something I need to do to calibrate or clean this?

Thanks in advance for any ideas.

How long have you kept the tag indoors? It can take a very long time for the tag to dry up to reach <100% relative humidity, especially when the enclosure is closed since the breathing sticker causes the humidity to change really slowly (which is not an issue under normal conditions when the humidity changes slowly anyway)

I live in southern Finland and here it’s rather typical for the humidity to be around 100% continuously for a very long time during the winter, and it can take many days after rain to drop below 100% when kept outdoors. Obviously the tag should dry up faster than that if kept indoors

Thanks for the reply.

It’s been indoors for a few hours and the temperature resolves quite quickly.

The Humidity is still sitting at 100% even though I’ve removed it from it’s housing now as the breathing sticker on the case is quite dirty.

I would expect it to match the humidity of the other tag it is beside indoors. How long should that take?

I would expect the humidity to start to stabilize within a few hours of removing the tag from its enclosure. If it hasn’t changed after a day then I would start to suspect damage to the sensor.

I once had a tag stop working completely due to excessive condensation inside the tag, after bringing it indoors (and out of its enclosure) for about 3 hours the tag came to life again. The humidity readings dropped below 100% a few hours after that, though the readings were still off, likely due to contamination in the sensor. It’s also worth noting that this particular tag was an older one which used a Bosch BME280 sensor, the newer tags have Sensirion SHTC3 sensor, so the exact behavior likely differs a little.

Take out the battery for a short time (power reset) already tested?


I did try that to no avail.
However, later today after about a day indoors, it had dropped back from 100% and is reading more like it should.

Can the sensor get so saturated that it would need to be dried out for an extended period?

Very long time in outdoor and very humid conditions will saturate humidity sensor readings. When the outdoor humidity goes down and sensor dries, it will disappear. Another way to fix this faster is to take sensor circuit board (no battery, no enclosure) to normal oven, 100 Celcius 2 hours. It should fix the sensor back to the original calibration state.

Thanks, that makes sense and it does seem to be drying out over time back to calibration baseline.

I have had this very same “humidity stuck at 100 %”, see screenshot. I have had a sensor outdoors for 2 years maybe, and last year it got stuck at 100 %. The plot shows that it has hit 100 % regularly. I have not tried baking it yet. Maybe next time I bake a cake, or warm up the sauna.

I guess RuuviTag is like a cat, and that microwave is not a good idea for curing it :slight_smile:

Again with the Sauna

Yes Mikko, normal oven is good to try as Henri mentioned above.

HI again, I did try to cook it in the oven at 100C for 2 hours. That has not resolved the issue with persistently high humidity from the sensor, unfortunately.

That’s interesting. Is the sensor showing all the time 100% humidity or when you have installed again to outdoors?

Hi Henri,

I’ve kept it indoors beside another temp/humidity product for comparison.

The humidity is not sticking to 100% but is holding higher than the actual environment it is in.
I have also removed the top cover since the case got dusty over its time outside.

The Ruuvitag readings of RH vary between 80-100% when the conditions indoors are really around 60-80% range.

I’ve got it linked to Home Assistant and have several temp/humidity sensors indoors, including another RuuviTag so I am confident of the discrepancy in readings.