Reccomendation for reliable humidity sensor for outdoor use


I ve using a BME280 sensor module within a Stevenson shield install in the roof to monitor humidity and temperature as well as pressure readings.
However it seems that the sensors fail and I need to replace the sensor every few months.

Does anyone have better experience with any other sensors or any recommendations?

How exactly does it fail? Unresponsive on I2C? Implausible values? Do you use it outside the specs?

I2c no longer responds.

Interesting. Where do you live? What weather conditions do you usually have? Is condensing humidity a problem?

I use a BME280 for years in an outside box so some conditions may be different at your site. Are you sure you use an original Bosch sensor? I recently saw a board sold as BME280 but containing a chip without the Bosch logo on it. Cheap Chinese clones tend to fail much earlier.

Yes i am in southern Europe and lately humidity has been measured at 100% by this sensor during early morning hours. Summer temperatures have also reached 40 C this year.
Sensor modules were bought on ebay....

I am now thinking to try the Dht22 sensors...

I have read bad things about the DHT11 and DHT22 in outdoor situations.
Some humidity sensors, like the Si7021, have a built-in heater. Which you can activate (with code) when the humidity is close to 100% (condensation). Make sure you get the one with the white (protective) teflon cover on the chip. For extra protection you could cover the whole board in epoxy, and only leave the white window exposed.

I would love to find a source for the white cover on the Si7021 with a goal to put it on an BME280.
I've worked with Gore filters before but no longer have a contact there.

It's AFAIK just teflon. The stuff plumbers use (thin/white plumber's tape).
The only problem is that you can't glue it.

I'm pretty sure it is expanded resulting is a porous structure. Large enough pores to allow vapor through but too small to allow water to pass.

Something like this "sintered PE"

When I get two BME280's running I'm going to try Tyvek

I use several BME280 sensors for my home monitoring project. They are all in plastic project boxes that have "pneumatic muffler filter silencer sintered bronze" (ebay search term) inserted in the bottom to allow the flow of air but keep bugs out and they have worked well for 2+ years.

I had noticed that sometimes the BME280 sensor would not return correct values for one of it's parameters (Temperature, Humidity, Pressure) and would just return NaN using the Adafruit library and I would have to power cycle it to fix the problem but I adapted the code to check for this situation and reset the BME280 sensor with the below code and this cured the problem.


Is this installed outdoors?

Does the "pneumatic muffler filter silencer sintered bronze" affect readings of humidity?

Post a picture of your weatherstation.

The sensors are installed indoors (one in each room) and outdoors.The silencer does not affect the readings as in the early days I ran one of the indoor modules in parallel with a bare (open to the air) BME280 and the values tracked each other quite well.
As they are battery powered I take rolling average readings every 10 minutes and transmit this value (over LoRa) every 30 minutes to give me about one year life with a 18650 battery. Humidity changes responds quite quickly as when we have to hang laundry in the house to dry you can see the room humidity levels change within an hour or two.

The outside sensor in is in a place where it has little chance of rain falling directly on it but it can get wet in very windy conditions. The silencer is facing downward to prevent water ingress and after 2+ years outside the only corrosion are the screws holding the case together and a little bit on the antenna connector. The internals (battery holder and electronics) are showing very little signs of damage/rust.


Just ordered Si7021 to try my luck with it..

Thank you for this suggestion :slight_smile:

Have you had any of the outside "bronze mufflers" start to turn green? I was looking through eBay and there are stainless steel versions for about 2x the price of bronze.


I have not had any visible corrosion on the outside muffler in 2+ years

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Not sure your PCB implementation, however I would take a failed unit, Put some scotch tape over the hole then wash the board with warm water and soap. Rinse well with warm water and dry the best you can. ESD aside, I use a short blast from my compressor.
Allow to dry and retest.

I suggest warm water as opposed to hot because I don't know what pressure trapped air in the sensor will reach if heated too much.

If that resurrects your sensor I would suggest a silicone conformal coating spray. Some folks like urethane but I prefer silicone as is is softer and less likely to stress the components. Acrylic works as well.

I always wondered how a HomeDepot can of Minwax Clear Urethane spray would work. Never tried it but still wondering.

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