- Technical Blog From My Notebook

Sunday, June 19, 2016

Light meters or illumination meter./Lux meter

Light intensity is measured by means of a light meter or illumination meter. You might think that its easy to make this kind of meter by connecting a milliammeter to a solar (photovoltaic) cell. And this is, in fact, a good way to construct an inexpensive light meter (Fig.).

 More sophisticated devices might use dc amplifiers to enhance sensitivity and to allow for several different ranges of readings. One problem with this design is that solar cells are not sensitive to light at exactly the same wavelengths as human eyes. This can be overcome by placing a colored filter in front of the solar cell, so that the solar cell becomes sensitive to the same wavelengths, in the same proportions, as human eyes. Another problem is calibrating the meter. This must usually be done at the factory, in units such as lumens or candela. Its not important that you know the precise definitions of these units in electricity and electronics.

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