Thermoplile interfacing to PIC

I want to get a PIC-based non-contact temperature sensor built to check the relative temperatures of wheels and tyres on heavy vehicles.

Do I treat the thermopile in a similar way to a thermocouple?

Should I take ambient temperature into account, remebering that it essentially the DIFFERENCE in wheel temperatures that is of interest in this application?

Azaruk said:

I want to get a PIC-based non-contact temperature sensor built to check the relative temperatures of wheels and tyres on heavy vehicles.

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Did you mean "wireless sensor"? If I understand it correctly, the thermocouple is a contact sensor.

Azaruk said:

Do I treat the thermopile in a similar way to a thermocouple?

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Yes, you do. But, may be, the thermopile could use less signal conditioning. Why are you using a thermopile instead of just thermocouple? Are you also going to use the thermopile to obtain power for the sensor?

Azaruk said:

Should I take ambient temperature into account, remebering that it essentially the DIFFERENCE in wheel temperatures that is of interest in this application?

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Yes, you should. You need cold junction compensation. There are a few ways to do it.

A thermopile produces voltage .So you have to amplify it first .Usually the manufaturer has an app note that show how to use it ! I think is better to use some kind of instrumentation OP amplifier .
also it needs lenses to concentrate the heat radiation on the sensor

eltonjohn said:

...also it needs lenses to concentrate the heat radiation on the sensor

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Wow. I can imagine a lens mounted onto a wheel of a heavy vehicle. It should also track the sun as the wheel pivots. Such device would look extremely cool.

these are called IR lenses .. not the regular type of clear lenses .But they are necessary

eltonjohn said:

these are called IR lenses .. not the regular type of clear lenses .But they are necessary

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Interesting. To my ignorance, I've never heard about them. But I did brief search on Wikipedia and Google. It looks that the IR lenses I could find would cost a lot. Could you give me a link to some app notes or intro information on IR lenses.

Without knowing more about the IR lenses, I would think that the practical problem with these lenses on a moving vehicle is that they have to be pointed to the sun. That would require 2 actuators.

Added after 3 minutes:

By the way, here's a thread from another forum with some historical background on thermopiles: https://forum.allaboutcircuits.com/showthread.php?t=4719

This is what you NEED

https://www.display-optics.com/products_passive_infrared.asp

The thermopile sensors (by Melexis) have integral IR lenses/filters. They are non-contact devices, similar in concept to a rudimentary camera, reacting to radiated infra-red energy and generating a voltage proportional to IR wavelength.

With my total lack of knowledge in all things PIC, I need help to convert the reading from the thermopile, less the ambient temperature (LM35) and display the result on a 7-segment LED display.

The thermopile voltage would be amplified to a useful level before sending it to the PIC for processing.

hey guys , actualy am workin for a distance temperature measurement for humain ,
its too hard usin 1 m dis without laser orientation ,
so i choose 30 mms for ma project ...and i get : ZTP-135 SR
, for Ge and am buildin its compensated circuit , in any why i will try to fix ; 50 mv/ deg c ...its hard for its calibration ....
please if there is any one understand good whot is the relation beween the thermistor and the thermopile and exactly ; why they do " defferentiel amplifier "
i mean for whot reason ! , i read many PDFs and i see that it used to get a clear humain radiation , but idono why they do (Uth - Uthmistor).. thanks