Using a Gore Vent for a BME280 sensor?

Hi

I am trying to use the BME280 in a project that will be outdoors. The challenge is therefore allowing water vapour in (to allow the sensor to detect humidity) whilst protecting the electronics from water damage.

It seems one solution is to use a Gore Vent. For example, see the Ruuvitag which uses the BME280 and includes a "Gore IP67 certified vent membrane".

Thinking about it, I was wondering how this works. Doesn't a Gore membrane only allow water vapour to pass one way? That being the case, wouldn't water vapour either get in but not get out or not get in at all?

Any recommendations as to Gore Vents welcome.

Thanks

Where did you get the idea that the membrane passes water vapor only one way?

Keep in mind that there is a large difference in energy between liquid water and water vapor.

My BME680 is outside and exposed to the elements but protected in a Stevenson’s Shield.

Why would you need anything else?

Gore membranes in general allow vapor through but not liquid. I have looked at gore membranes for my (now stalled ) BME280 sensor but was concerned the stabilization point of any of the three measurements might be shifted due to the membrane that I figured I'd go with is essentially the Stevenson Shield.
If the environment damaged the sensor I would try something else next time.

With a Gore membrane you're going to let in humid air, the moment the temperature drops that will lead to condensation inside your enclosure (it's not that water vapour passes quickly or so!), which has no way of escaping. The reaction time to changes in humidity will also be huge if you close it off like that. Such a screen is likely going to make your problems far worse than with a regular Stevenson's screen or using an inverted bucket.

wvmarle:
With a Gore membrane you're going to let in humid air, the moment the temperature drops that will lead to condensation inside your enclosure (it's not that water vapour passes quickly or so!), which has no way of escaping. The reaction time to changes in humidity will also be huge if you close it off like that. Such a screen is likely going to make your problems far worse than with a regular Stevenson's screen or using an inverted bucket.

Thanks. So is there no reliable way to measure humidity, temperature and pressure when the sensor is in an enclosure?
At the moment, I have a small enclosure with the microcontroller and a battery. Adding a Stevenson shield would significantly increase the physical size of the project (and make the project much more conspicuous!).

Of course the only way to reliably measure that is if there is a free exchange of air with the outside environment. Otherwise you're measuring something different - just like inside your home temperature and humidity are different from outside.

An inverted bucket can be made really small, down to a little larger than the size of the electronics themselves. Just make sure there's no possibility for splashing, or wind blowing the rain in.

Measuring the what-not during rain

and doing the thing in the snow:

There is a way.

I have small enclosures outside with BME280 for a couple of years and use brass silencers like these to allow airflow. They (the silencer) are facing downwards so rain cannot enter. They also seem to be very good at deterring insect ingress