Thermopile

Hi,
I am trying to build a circuit for detecting infrared radiation using a thermopile. I have a schematic of a circuit but I'm unsure of what it does. (see attachment file)All that I want to do is measure the voltage output of the thermopile. How do I measure the voltage output? I am presuming that the OP297's are there to add gain but i'm unsure why the LM358's are there. I tried building the circuit but in place of the OP297's I used LM324's. The circuit didn't work. Would the LM324's have made the difference between it working and not working? Is there any simpler circuit I could implement to see if the thermopile is actually working? I am really stuck with this as its part of my final year project in university and its due in soon.
Thanks for any help.
Ruairí

The circuit has a LOT of gain, so you have to have a low noise op amp at the front end. The LM325/358 is noisy but OK at the output end. ICB is used as a comparator. ICA just amplifies the Thermistor output which is not a low level signal.

i think the TL084 is better than , low noise , low offset ....

This circuit may be particularly sensitive to op-amp offsets, which are problematic to fix- they can shift with temp. There are low-offset opamps out there.
You'll need to know the signal level off the thermopile to begin with.

IIRC, the thermopyle's output is a difference between the TP temp and the target temp. Which is why there's a temp reference there to establish the absolute value of the TP's temp so we can determine the absolute target temp.

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 , use TL084 amplifier , 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

I think Oznog is right. The 324 has offsets in the mv range while the op297 is in the uv range. With gains in the 1000's it is probably pegged against one rail.