2-Color Temperature Measurement

Projects General Guidance
1

Hi All,

I am looking into a 2-color temperature measurement, and was trying to assess how feasible it is within my strict budget constraints.

The idea is to take two narrow band photo-diodes (e.g here) and to use the two measurements to calculate the temperature. My intentions are to connect each photo-diode to an Arduino (that is already in the system), and calculate the temperature on it.

Does anyone have any experience with such a thing?
Is this feasible?
How narrow band should the photodiodes be? Can I handle it without additional optical filters?
Is the price including amplifiers and periphery going to remain relevant (less than hundred of dollars, and preferably much less...)?

Thank you very much,
I would appreciate any input.

Background:
As part of my academic work, I am heating a thin stainless steel net filled with organic compounds to 200 deg Celsius. As I didn't manage to get a reliable temp reading using thermistors and thermocouples, I moved to a contactless sensor. Unfortunately, the residues from the heated materials in the system tend to cause the IR sensor to deteriorate. I am looking to apply a measurement that will not be dependent in amplitude, but rather in ratio. As this is an academic project, I have a very limited budget, and as I need several sensors, it would be better to keep costs very low.
The accuracy I need is rather low. Even a 5 degrees error is acceptable.

2

200 degress is not that high so I Googled for arduino thermocouple and found this useful link (shhh, on a competing forum):

Thermocouple Info

May give you some ideas...

3

How are you heating the wire net and what is the wire gauge?

Why do you think that the temperature readings you obtained with a thermocouple are not reliable?

4

I compared the thermocouple readings with a good IR camera. It is off by more than 30 degrees sometimes. I tend to believe the fact that I am using a steel net, and that it is very small prevents me from reaching a good thermal contact. Using thermal grease and other materials for better contact is not possible.
The net is made of wires that are about 50 microns in diameter.
Heating is performed by an electrical current through the net.

Thank you again for the help,