Hi everyone,
I have been working on a project to measure (among other things) the temperature on a balloon flight up to around 40km altitude. I've read some papers indicating that temperatures could be around -60C, but I would like some wiggle room; measuring to around -80C to -100C (if possible), with an accuracy of around 1C.
I began by searching through the various types of temperature sensors readily available through Digikey, Farnell, etc, and it seems to me that the use of a thermocouple would allow me to achieve these sorts of measurements. However, I come across the problem of selecting an appropriate reference IC, as these seem to be available down to only (!) -20C
http://www.digikey.co.uk/product-search/en/integrated-circuits-ics/interface-sensor-and-detector-interfaces/2556696.
I was wondering if anyone might be able to offer suggestions as to how I may be able to measure temperatures down to these ranges, bearing in mind the entire system will also be exposed to such temperatures. I am open to being told to scrap the thermocouple approach if needed.
I'm not too concerned about staying within manufacture's temperature tolerances, unless they actually affect the output significantly (eg; I have flown microcontrollers rated at -40C to temps below -55C before). I have a budget of around £30 (~$45 USD) for the temperature sensing circuit, but can go a little above if needed. Output-wise, just about anything is okay.
I hope I've written everything needed, and everything clear enough to be understood. If not, let me know and I will try to explain again.
Many thanks for your time in advance.
SF