Here’s design circuit for a Portable light-level meter circuit with five-decade dynamic range. This uses a single cell battery as the power supply. To calibrate this circuit, use an appropriate illumination, then adjust R2 so that the output equals the reference. This is the figure of the circuit;
To make this circuit give output meter follows standard light meter, adjust R2 and R6. Maybe there is an error at the scale extremes because the log slope is not temperature compensated. An infrared-stop filter is recommended for this circuit because silicon photo-diodes (D1) are sensitive to near-infrared light. This circuit will give a excellent results if an appropriate correction filter is applied and a blue-enhanced photodiode for D1 is used. [Circuit diagram source: National Semiconductor Application Note]
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