Weather Station / Data Logger

Hi all,

My uncle's job deals with making stations that record temperature, wind speed, wind direction and air pressure. He generally has to make these with large boxes 500 x 600 mm but I was hoping to make I much smaller. I need to have very accurate readings from all of those and use the GPRS shield to send that data. Generally they are solar charged but his usual boxes use 12v batteries so I was hoping to use some small Li-Po rechargeable batteries that can be charged with smaller solar panels, the housings must be completely weatherproof. I would be thankful for any help you can give.

Will

I have some boards at the fab shop for what I call my Weather Board, it will report air pressure, temperature and rel humidity on I2C. The overall size of the board is just over a square inch.

Keeping the price of the board down I made some choices of the sensors that may or may not meet your "very accurate" threshold. The accuracy thresholds may be a problem for relative humidity as the main need for the board was to measure the density altitude and humidity is least significant of the 3 measurements. You might want to tell us what "very accurate" means so then myself and others know if what have is good enough to help you out.

Being I2C for all the sensors it can easily be used with an Arduino and implemented with GPRS shield.

willhew:
I need to have very accurate readings from all of those...

What would you consider "very accurate"? 18 significant digits?

Two or Three decimal points about that accurate. Thanks Coding Badly, also does anyone have links to sensors I can use for this project

Will

1-Wire sensors are extremely easy to use, low power, inexpensive, and I believe accurate enough...

http://www.maximintegrated.com/products/thermal-management/

A note on using 2-3 decimal points as an accuracy metric or for that matter any figure of merit. Assume I make a measurement of a 1.0 centimeter this is 0.00010 kilometers. The first result has one decimal place and the second has 5, is the measurement any different by only changing the coordinate system?

You need to be a little more quantitative when making requirements on accuracy.

In my research on weather sensors it seems the humidity is hard to measure to within say +/-3% without spending a lot of money and doing occasional instrument calibration. Buying the equipment for calibration will drive the cost up very quickly.

When starting out on a design of a sensor system making it very accurate is always the initial response. Somewhere along the design process you need to ask yourself what it is you need to accomplish with the instrument and let that drive your accuracy requirements. In my first reply I talked about using a humidity sensor that was accurate to +/-5% and saying that was good enough for my application, density altitude measurement. Humidity's influence on the density is very small so I could get away with a lower quality measurement of it, ther +/-5% error on the humidity did not map over to a +/-5% on the density altitude.

On to sensors, for measuring pressure Freescale was a great line of MEMs sensor and I would encourage you to look at their website. MEMs sensors was dramatically driven the cost and size of the sensors down and you probably want to exploit that.

wade