Understanding Light Intensity through Light Meter

saoodhashimOctober 27, 2013

I download an android light meter application, that had good reviews from its users. My intention was to measure the intensity of sunlight during the day. From my discussion with "Art33", a GW member, whom I am greatly thankful to, could make out that the indoor readings under floru lights from my application and his "Dr. Meter" light meter were sort of giving similar readings. While not a pure scientific confirmation, it did help me in assessing the accuracy of the application.

The application works by receiving light rays into the small light sensor that is just besides the front camera of most android based cell phones. Now when I tilt the phone to face the sun, it always gives me maximum reading except for very early morning (i.e. within 30 minutes of sunrise. After which it reaches max reading of 12000 foot candles). However, as I move the tilt of the phone away from the sun and towards the sky, the reading keeps on reducing. These reading made me curious about light intensity. Now, unless you conclude that the application has any programming / other issues, I would assume that since the light sensor is very small, it can only provide the correct reading when it is facing the source of light and that is the correct reading when light intensity is being measured (especially when sun is the source of light)? Is it so?

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Useless in my opinion.
The only thing that comes close to being useful under $500 is the SQ-120: Electric Calibration Quantum Sensor from Apogee

I bought several light sensors and just gave up on their reliability and made my own calculations based on educated studies rather than useless measurements.

Read this pdf from Purdue

and this pdf from Cornell

    Bookmark   November 11, 2013 at 11:32AM
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