Alphasense sells this NO2 sensor:
http://www.alphasense.com/environmental-sensors/alphasense_downloads.html
http://www.alphasense.com/environmental-sensors/pdf/NO2B4.pdf
How can I read the values from an Arduino ? Do I need something between the Arduino and the sensor ?
I have used a few basic sensors before, but I'm confused with this gas sensor: why does the response curve seem to loop ? I naively expected a constant tension for a given concentration, but it looks like it is more complicated with chemical sensors.