Use of Sensirion temp module.

Rsadeika

I purchased, from Parallax, a Sensirion temp/humidity module which I have running on my breadboard. I am using the Propeller to access the module, and the question is, what kind of enclosure can I use to data log external temp/humidity correctly?

My first experiment will be to data log, 24/7, the environment in my attic, so the enclosure has to keep out any critters that my be present, away from the electronics. The concern that I have is, the module, being inside of the enclosure, will be reading the temp/humidity that is there. I can not put the module on the outside of the enclosure, exposing to the elements. Eventually, I will be moving the unit outside, and measuring some of the temps, so safe guarding the module will be paramount.

Anybody have any ideas for me as to what I can use?

Thanks

Ray

LoopyByteloose

I suspect that the actual sensor might best be explained by Sensirion documentation. Putting that in an enclosed space could vastly distort the results of both the temperature and the humidity. If you must protect it from bugs and rats, a bit of the kind of screen used on screen doors might be required. Having it hang from the bottom of the unit might keep the weather off of it and away from direct exposure to the sun. Wind chill is another factor with outside use, but I am not sure that the mounting has to deal with it. Placement of the device in the right location might resolve that.

Mike Green

Well, you have to expose the sensor to the environment so that you can get readings from the environment rather than readings for the inside of the enclosure. A lot depends on just how extreme the conditions might be.

You will need to mount the sensor so that it's not immediately adjacent to the Propeller and its voltage regulator so that the temperature of that doesn't significantly affect the sensor.

If you've got modest temperatures, say down to freezing, a glass jar will work nicely. You have to modify the lid so any cables exit through gaskets in the lid (silicone glue will do). You'll need a hole in the lid, maybe 1/2 inch or so for the air to enter (along with water vapor) covered with some kind of coarse cloth to keep out dust and critters ... with the sensor mounted just above the hole. The rest of the electronics should be mounted towards the other end of the jar with some insulation between the sensor and the electronics. Cotton wool will work or a wad of loose yarn. The jar has to be mounted upside down with some stretchy electrical tape around the edge of the lid to keep water out. You could even make an apron using some plastic tape or thick film to further keep water away from the sensor hole and connections.

RDL2004

For outdoors, what's often used is called a Stevenson Screen. There are many variations. If you google a bit you will find lots of home-built projects where people have made their own.

Tracy Allen

You could make a small hole (2mm) in the enclosure and put the sensor opening right up against that. Or, Sensirion offers a protective cover (SF1), made of polyethylene with a gortex filter membrane that fits over the sensor. You can see in the SHT11 data sheet how that is arraged. It has a round top that can be pushed up through a hole in an enclosure sealed with an O-ring.

I was thinking you could mount the electronics in one of those hi-tech breathable gortex shoes, but if there are "critters" running around, they would probably carry it off or chew it up!

Franklin

http://www.ambientweather.com/amwesrpatean.html made for weather stations.

WBA Consulting

As mentioned, the Sensirion SF1 (which is available through Newark as P/N 09J2305) makes it easy to protect the SHT11 and SHT15 line of sensors. If you look at the gallery page on my retired SHT11 Module's site, you will see a couple pictures of the SF1 cap in use. Unfortunately, you can not mount it directly onto the Parallax version because of the header pins. However, having it spaced slightly away from the sensor to accommodate the headers will only slow down the response time of the sensor (which will be slowed down in any enclosure).
Depending on the environment, simple "protected exposure" will be just fine. As an example, the attached picture is the first enclosure version of a product that uses an SHT11. The round holes are for a power supply and a 2.4ghz antenna. The slits are the access for air and water vapor for temp/humidity measurements. Keep in mind however, this was used inside buildings.