For determination of illumination take the light meter, bring its sensor in the necessary point of space and take off data from its scale or the screen of the display. The second way by which it is possible to measure illumination – by means of a selenic photo cell and the milliamperemeter attached to it. Also the illumination of a surface can be calculated if source luminous intensity is known.
It is required to you
- dot light source, selenic photo cell, milliamperemeter and light meter, protractor, range finder.
Instruction
1. Measurement of illumination the light meter Take the light meter and install its sensor on a surface which illumination is measured. At the same time surely track that the plane of a photosensitive element of the sensor was surely parallel lightto surfaces lit by a source. After that take readings from a scale of the analog device or the display digital is and there will be an illumination of this surface in luxury.
2. Measurement of illumination from a dot light source Include a dot light source (it is such source, which sizes negligibly piers in comparison with distance at which measurements are performed). It can be a usual lamp with in advance known luminous intensity in candelas which can be found in the reference book. After that at some distance from it (it has to exceed considerably its sizes), place a surface which illumination needs to be measured. Measure distance from a light source to a surface in meters in any available way. It is possible to use a usual roulette or a range finder of any type. Then measure a corner under which rays of light from a source on the lit surface fall. For this purpose restore to it a perpendicular and by means of a protractor or the same range finder measure a corner between a perpendicular and the falling beam. Calculate illumination. For this purpose divide luminous intensity into a distance square to a source, and increase the turned-out result by a cosine of the angle of falling of a beam (E=I/r²\• Cos(α)).
3. Determination of illumination by means of selenic you fotoelementaprisoyedinit a selenic photo cell to the milliamperemeter. Insert an empty scale into the milliamperemeter and having darkened a photo cell, make on it line which will mean zero illumination. Then, having calculated illumination, by the technique stated in the previous point, establish a photo cell in a point with the known illumination. The ampermeter will show existence of current, and his shooter will deviate. Deliver to the devil on that place of a scale where the arrow stopped and specify not by it illumination in luxury. Then graduate a scale, dividing it into proportional parts. As a result the self-made light meter by which it is possible to measure illumination will turn out.