I've been trying to use my arduino as a thermal anemometer based on the excellent and tiny IST FS5 "thermal mass flow sensor" - there is more information and a datasheet here - http://uk.farnell.com/ist/fs5-0-1l-195/sensor-flow-gas/dp/1778049. I've set up the circuit as recommended in the data sheet, albeit using a different op-amp and transistor (and excluding the calibration resistor) and it seems to work nicely. The only problem is the output is between 5 and 10V, and obviously the arduino likes something in the 0 - 5V range. I've used a simple voltage divider to scale the voltage between 2.5 and 5V, but it would be nice to use the full range... unfortunately my electronics knowledge is far too limited for this!
I've read some similar forum posts and tried to use a 5V voltage regulator and another opamp to produce something useful but failed miserably! I'd really appreciate it if anyone could give me some hints on how to use an op-amp to achieve this. I feel like it also must be possible to change the wheatstone bridge arrangment so as to produce this voltage range in the first place, but have no idea how!
schematic here - http://dl.dropbox.com/u/7549930/aaSchematic1.png