IR intensity measurement

Hi ,

Can anyone tell me a IR sensor or a logic which gives an output voltage
propotional to the intensity of the incident radiation.

My transmitter is a 940nm IR LED. And i have tried many sensors
like TSOP 78xx , but here it detects the radiation. The output
merely says if the IR radiation is present or absent.

The basic block is as follows :

IR Transmitter -> Sample -> IR receiver -> Signal processing

The Sample is an medium which has peak absorbance at 940nm.
Hence the source is IR radiation.

I have tried some alternatives like capturing the image by digital
camera.., but i
would like to have a simple measurement.

regards
partha

 

[Rich]

A silicon photodiode followed by a transimpedience amp would do the
trick.
check out:
http://www.ecotechnologies.biz/ebay/si_pd_circuit_examples.pdf

 

[Rich]

Looking at example 12 in the pdf file, you may be able to just use an
ammeter. All depends on what your trying to do, ie, lab experiment or
stand alone transmission monitor.