# Solar light intensity measurment

Hello! i have a question.i am working on my final year project Data logger of solar tracking system in which i logged solar light intensity (lux) but i am facing problem .i have already used LDR and different sensors.problem of LDR is non linearity and sensors that i used are limited calebrared for example A sensor BH1750 Wide range and High resolution is ( 1 - 65535 lux ).but in my project i need a sensor that can measure solar light intensity between(50000-150000) lux .Please tell me any method for measurement of solar light intensity?

Hey,

If you would like to measure a light intensity of 50,000-150,000 lux with a sensur with a range of 1-65,535 lux, you can use a semi-transparent filter that only let parts of the light through. If you direct the sensor directly at the sun so you get unpolarized light, you could for instance use two polarization filters at 35 degrees to let through about 1/3 of the intensity by Malus's law. (Be careful, if you direct it away from the sun, you will get polarized light from the sky.) This will map the 50,000-150,000 lux to a 16,700-50,000 lux range which your sensor can measure.

To deal with a non linear sensor, need to find a non linear function to map your input values to the correct intensity. A second orden polynomial will often be sufficient, but it will depend on the sensor and your desired accuracy. After deciding on the form of the function, you need to measure the input for a number of different known intensity sources or look at a graph provided by the manufacturer of the sensor and to do regression to find the unknown constants in your function. You can also just to linear regression between each measured point.

Hope this has been to some help

Light intensity is logarithmic. An LDR will in most cases do just fine.
One can use two or three of them, with different series resistor, for better precision