Notes:
As I was developing my IR
Extender Circuit, I needed to find a way of measuring the relative
intensities of different Infra red light sources. This circuit is the result
of my research. I have used a photodiode, SFH2030 as an infra red sensor.
A MOSFET opamp, CA3140 is used in the differential mode to amplify the
pulses of current from the photodiode. LED1 is an ordinary coloured led
which will light when IR radiation is being received. The output of the
opamp, pin 6 may be connected to a multimeter set to read DC volts. Infra
red remote control strengths can be compared by the meter reading, the
higher the reading, the stronger the infra red light. I aimed different
remote control at the sensor from about 1 meter away when comparing results.
For every microamp of current through the photodiode, about 1 volt is produced
at the output. A 741 or LF351 will not work in this circuit. Although
I have used a 12 volt power supply, a 9 volt battery will also work here.
Source: http://www.zen22142.zen.co.uk