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IR Thermopile OpAmp

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binux369

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I research IR measurement temperature for my study minithesis to obtain engineer degree of university and I use IR thermopile
I have a standart thermopile detectore TO-5 Single-Channel Thin Film Based Thermopiles
I was tray use IC OP177 opamp prcesison integral n inverting but output in OP177 no ressponding.
can help me any design opamp for thermopile sensor.

thenks
 
The thermopile I looked up has an output of 40uV/deg K. This requires an op amp with a very low input offset and your OP177 would be good for this with an offset of 25uV max @ 25C. BUT, your OP177 was designed and specified for +/- 15V operation, which is probably more than available in your circuit. In fact, the common mode range for this op amp does NOT include the V- supply, so if you use a 5V source and gnd the supply and thermopile at the V- terminal, the circuit will not operate.

Unless you have the +/- 15V available, you need to replace the OP177 with a similar low offset op amp specified for 5V operation (or maybe 12 if it is powered by a car or some larger supply) and be sure it also has low input noise. Also look for a high output voltage- many can only output 3V with a 5V supply, if it is specified as "Rail-To-Rail Output", it can give you 5V.

Correct me if I'm wrong, but the thermopile puts out a negative voltage if the target is colder than the thermopile, right? In that case, you'll need to make up a low noise bias point at 2.5V to act as a ground.

You still may need noise filtering, I expect that thermopile may be a noisy sensor. In that case, the op amp noise may not be an issue, you'd just use it as a preamp before the noise filter.

Be aware you MUST use the cold junction temperature to compensate the output. The signal itself is only the difference between the target's temp and the thermopile's 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
 
PLease do not do that.


Hijacking a thread that way is a bad thing. You will confuse the issue and a search at a later time will give a confusing result.

Start one by yourself.
 
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