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Topic: Finding sensors best suited to weather station project (Read 2 times) previous topic - next topic

MrGarak

Ok, so I am very new to arduino (don't even have one yet) but have extensive programming and C experience (was a CS major). I've always wanted to have a weather station but have never liked the limitations and non-customizable nature of the commercial offerings. Once I heard about arduino I did a ton of reading up on it as it was an interesting subject for me, and it seems the perfect project for me to take on if I take the plunge into the arduino world.

Obviously I want to take the best approach when putting something like this together, and that has led me to researching what would be the best sensor solution for this type of project. There are a ton of sensors out there, but the two major categories appear to be the thermistor approach, and the digital sensor solution. I want as accurate sensors as possible while keeping the price reasonable. According to this site (scroll to the very bottom), the best accuracy you can hope for from an arduino using the analog approach would be half a degree centigrade. I'd like something with at worst +/- 0.1C accuracy, along with a fast response time. Would an infrared temperature sensor be a feasible approach for this type of application? I also found this integrated humidity and temp sensor, but could not find any datasheet on its accuracy for temperature and humidity. My concern with humidity sensors also is their tendency to go bad after a while. I remember the oregon scientific weather station humidity sensors were notorious for this problem. Therefore, if possible I'd like to get a humidity sensor that has a decent lifespan instead of only a year like the OS ones, and is accurate enough for a good dewpoint calculation. Anyone have ideas on decent sensors that would be well suited to the arduino?

I'm not going to pursue other sensors besides temp, humidity, and barometric pressure one for now. The rain gauge and wind sensors I can always add at a later time.

MrGarak

OK, I found the datasheet on the dht22, I wasn't thinking and hadn't tried searching for it. It appears it's +/- 0.2C. I've also been unable to find humidity sensors with better than +/- 2% RH accuracy (perhaps the tech just doesn't exist). After doing some more research, it appears a 0.1% accurate thermistor could approach 0.1C accuracy on the arduino, the big limitation being the arduino's ADC. I haven't been able to find dedicated arduino thermistor reading boards.

copiertalk

I have thought about building one I am not not commited to buying the components yet.

http://us.oregonscientific.com/cat-Weather-sub-Professional-Weather-Sensors-and-Extra-Displays-prod-Professional-Wind-Sensor-with-Poles-and-Complete-Mounting-Kit.html

Sparkfun had a rain guage / wind cup/direction sensor at one time but the last time I looked they were sold out.

MrGarak

#3
Sep 07, 2012, 07:12 am Last Edit: Sep 07, 2012, 07:14 am by MrGarak Reason: 1
I figure someone might ask why 0.2C isn't good enough. In a weather situation, especially with things like freezing rain, you want something accurate to at least a tenth of a degree fahrenheit. 0.1c == .18 fahrenheit, so even that is outside the desired range. Ideally, I'd like something that could take advantage of a 0.1% 10k thermistor, but haven't found such a solution yet for the arduino. It may be I'd have to go with a different microcontroller entirely, which would be a shame since the arduino seems like such a newbie friendly way to get into microcontrollers.

Thanks for the info copiertalk. To be honest I'm wary of going with OS stuff, given my experiences with them along with what I've heard from friends who've had even their higher end weather stations. Their stuff tends to have QC issues, are unreliable, and prone to failure. I had my eye on the sparkfun anemometer package but I just want to start out with the basics (temp sensor, pressure sensor, fan aspiration, relative humidity sensor, and possibly a wireless solution for outside siting) to begin with, and then possibly add things like anemometer and rain gauge down the road sometime.

MrGarak

Hate to keep replying to myself here, but I've found that probably the best approach to get the accuracy I want (+/- 0.1F or better) is to get a 12 or 16bit ADC and hook up the thermistor to that, and then the ADC to the arduino. Unfortunately this process seems a bit much for someone who has no microcontroller experience, unless I'm missing an easy plug n play ADC for arduino shield out there.

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