It's likely you'll get a useable signal out of this. You also might want to use the other end of the LM358 as a slow comparator with a 10K pullup at the output to give you a CMOS-compatible logic signal.
I'm also not sure what you mean by an "infrared body". Possibly you might want to try just sensing the flame coming off a cigarette lighter first, to see if your sensor works. The data sheet says your sensor is selective as to response frequency, with a 5um long pass filter. If you're using an narrow band infrared source (like an IR LED), it might be the wrong frequency to respond.
Is any of this relevant? If not, could you describe what you're doing with the FET output of the sensor, and what you're sensing, in somewhat more detail?
--- The detector is doing just what it's supposed to do, which is to sense a _change_ in temperature and produce an output when it senses that change. What's happening is that when the sensor heats up it sends out a voltage of one polarity while it's heating up, and then when it starts cooling down it sends out a voltage of the opposite polarity while it's cooling down. During the times its temperature is steady, it does nothing.
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--- If you're getting _any_ output from the detector, chances are there's nothing wrong with it.
thank you so much for ur suggestions. I will try to sort it out the way u said. I think it is doing wat it has to do. Chris, I am trying to use it as a motion detector. i.e to detect the infrared radiation from our body. so it shud produce a pulse wen someone pass throu.. say across a particular door. I am using a dual element PIR. I will soon get back to you with my output. thanks again for ur reply.
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Actually, it\'s Drain, Source and Ground.
Note that the power supply is connected between the drain and ground
and that the output signal appears across the source and ground.
The gate of the FET is connected internally to the free end one of
the series-opposed connected pyroelectric transducers, with the free
end of the other transducer connected to ground. They\'re connected
in series-opposition so that, for ambient temperature changes,
they\'ll be inherently self temperature-compensating, while when a
differential thermal signal hits one transducer the charge generated
will be placed on the gate of the FET and converted to a voltage
before it exits the package.
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