Note: An updated version of my code is available at /2012/11/update-reading-data-from-a-sensirion-sht1x-with-a-raspberry-pi/
The Sensirion SHT1x range of sensors provide a rather convenient way to accurately measure Temperature and Relative Humidity.
They aren’t the cheapest sensors as they typically sell for around $40, but they seem very accurate. I obtained a Sensirion SHT11 a while back as a free sample. I’d managed to get it working with an AVR ATMEGA328P for a planned project to build an Incubator, but now I wanted to read data from it using the GPIO of a Raspberry Pi.
I decided to keep the SHT11 allocated to my Incubator and bought an SHT15 for my weather station. The sensors are very similar. The data sheet shows that the SHT11 has an accuracy of ±3% Relative Humidity and ±0.4° Centigrade while the SHT15 is slightly better at ±2%RH and ±0.3°C. The communication interface is identical so no problems changing sensors in the future.
Before you can use my code sample, you’ll need to get the latest BCM2835 Raspberry Pi GPIO Library from http://www.open.com.au/mikem/bcm2835/ and wire up the sensor to the Raspberry Pi GPIO port.