# Infrared phototransistor to infrared thermometer

 P: 3 I am designing a tyre temp monitoring system for my Final year project and I would like to know if it is possible to somehow modify a infrared phototransistor to be able to measure an objects temperature in a range of -20 - 120 C. Any suggestions would be greatly appreciated.
Mentor
P: 41,088
 Quote by Moses Freeman I am designing a tyre temp monitoring system for my Final year project and I would like to know if it is possible to somehow modify a infrared phototransistor to be able to measure an objects temperature in a range of -20 - 120 C. Any suggestions would be greatly appreciated.
Welcome to the PF.

Can you explain a bit about how IR thermometers work?
 P: 3 I have a basic knowledge of how they work: Objects with temperatures above zero kelvin emit electromagnetic radiation in the form of waves, the radiation between 0.7umm and 20umm is collected by the lens of the thermometer which is then focused onto the sensor. The output is an electrical signal which is then worked out to find the temperature. I am not too sure about the internal circuitry but I believe they use a few differential amplifiers for the temperature compensation.
Mentor
P: 41,088
Infrared phototransistor to infrared thermometer

 Quote by Moses Freeman I have a basic knowledge of how they work: Objects with temperatures above zero kelvin emit electromagnetic radiation in the form of waves, the radiation between 0.7umm and 20umm is collected by the lens of the thermometer which is then focused onto the sensor. The output is an electrical signal which is then worked out to find the temperature. I am not too sure about the internal circuitry but I believe they use a few differential amplifiers for the temperature compensation.
As the temperature of the object changes, what changes about the IR light coming off of it that is used to figure out the temperature?
 P: 3 I believe the change in energy is converted to an electrical signal that is displayed in units of temperature after being compensated for ambient temperature variation.
P: 236
 Quote by berkeman As the temperature of the object changes, what changes about the IR light coming off of it that is used to figure out the temperature?
Frequency?
Mentor
P: 41,088
 Quote by Moses Freeman I believe the change in energy is converted to an electrical signal that is displayed in units of temperature after being compensated for ambient temperature variation.
That's not very specific, nor very accurate. What reading and research have you done so far on the subject? This is *your* project after all, so you should be doing the reading to gain a basic understanding of how these things work.

Please do some reading at wikipedia and/or HowStuffWorks, and then tell us in better detail what the mechanism is behind IR thermometers...
Mentor
P: 41,088
 Quote by perplexabot Frequency?
In case you hadn't noticed, I'm trying to get the OP to actually do some work here. Please let him do some research and get back to us. Thanks

 Related Discussions General Discussion 8 Electrical Engineering 2 General Physics 8 General Physics 15 Electrical Engineering 1