Hi, everyone,
I bought the tsl2561 luminosity sensor but when comparing the outcome values with a standard digital light meter, the accuracy is around 75% to 80% (more light = more accuracy), which is a significant percentage for me. I'm using the sensor connected with Arduino UNO to measure the daylight value for a room (which eventually will determine how the mechanical louvers will rotate to block the light if its too bright), where I need something with accuracy level of (+- 10% max).
Its an illuminance/irradiance sensor, not luminosity. It can only measure the light per unit area falling on it, not the total light output of a distant object.
Luminousity - total output from a light source, unit: lumen
Luminous intensity - light output per unit solid angle from a source, unit: candela
illuminance - the light falling on a surface/sensor per unit area, unit: lux
The difference you are seeing is probably due to different spectral profiles of the two sensors you are comparing. Or you simply haven't calibrated it - the datasheet implies it has very wide device variation. Or you aren't using the right diffuser. There are lots of sources of error possible with a light sensor.
If you believe the "standard digital light meter" then try calibrating the TSL2561 sensor against it, under a wide range of light conditions. That way you can determine the problem, if any, and also if a non-linear correction is justified.
