Measurement of the illuminance using a Signal Conditioning Circuit.

Measuring the illuminance of light is needed in a lot of applications such as in the corrosion mapping of steel surfaces, in distance measurement and also in analytical ultracentrifuge. Illuminance is a measure of the perceived power of light per unit area. It is a measure of light intensity that is perceived by the human eye. When light with different illuminance is incident on a Light dependent resistor (LDR), its resistance varies according to the illuminance of the light falling on it. Making this LDR a part of a Signal conditioning circuit, we achieve an output voltage which depends on the change in the resistance of the LDR. Hence, by measuring the output voltage, the illuminance of the incident light on the surface is obtained and we establish a relationship between illuminance on the surface of the LDR and the distance of the light source..