jluciani ~ not sure what you mean by .5% - 1%, are you referring to CO2 concentration, I'm trying to differentiate with a resolution of 50 ppm minumum, which is .005%! I'm designing a CO2 controller that will be used in a greenhouse to take the ambient CO2 from 300PPM to 2000PPM, so I'm looking at a fairly narrow range. I'm also thinking I'll need at least one full step of resolution in between the trigger level and releasing the trigger, and as one of the goals here is to maintain as stable of an environment as possible, I want this to be as small as possible.
If I get what you mean by '100x' 'instrumental amplifier', that's what I was leaning towards; I ordered a 10 pack of TL062 the other day for the pH probe I'm also going to try and cobble together. I have an inkling of how to use these, but no experience with them yet.
I briefly looked into those two sites, but instantly I was turned off by appliedsensor's front page "We'll use our intellectual property, proprietary software tools" ... yeah, no.
I'm trying to make this as open source as possible; that phrase just turns me off. e2v looks a little more promising... even though some of their documentation says for IR11BR it measures between 0% and 100%, in the
more generic datasheet that covered the whole product range stated the IR11BD and IR21DB sensed 0-3000PPM,0-2.0% vol, and 0-5.0% vol... that might need a little further investigation, but for now, I think the sensor from Futurlec (MG811) will work fine.
retrolefty ~ "Use the analogReference(INTERNAL) command to make the Arduino measurement range around 0- 1.1vdc. This would give you around one step per millivolt resolution. http://arduino.cc/en/Reference/AnalogReference"
Thank you!!! If my math is correct, with a difference of 1700PPM being represented by a change of 39mV, a 1mV resolution would equal around 45 PPM per step. Still a little higher than I would like, but hey, this will work!