Take the light meter, install its sensor in a space point where illumination is measured, on the display or a scale take off data. If this device is absent, take a selenic element, the milliamperemeter, previously having calculated illumination from a dot source with the known luminous intensity.
It is required to you
- the light meter, selenic photo cell, the milliamperemeter, range finder, with a possibility of measurement of corners.
Instruction
1. Measurement of a luxmetromesla it is necessarysearchof illumination of some surface, install on it the light meter sensor. Beams at the same time have to fall on it under the same corner, as on the measured surface. If a surface uneven, place the sensor on a tangent to it. On a scale or the screen of the device there will be indications in luxury which needs to be recorded.
2. Calculation of illumination from a dot source Establish a light source which sizes can be neglected (dot source). For this purpose use a special lamp which luminous intensity find in the reference book. At the distance considerably exceeding its sizes measure the illumination of any surface. By means of a range finder measure distance from a point in which illumination to a source and also a corner under which beams fall is measured. For this purpose, from 90º take away the measured corner of beams to the horizon. Then calculate value of illumination. Divide the luminous intensity measured in candelas into the distance to a source squared, increase result by a cosine of the angle of falling of a light beam of E=I/r²\• Cos(α).
3. Measurement of illumination Collect by a selenic element a chain from a semiconductor selenic photo cell and the milliamperemeter. Place a photo cell in that point of a surface where illumination was calculated. Cover it with dense black paper so that on it light beams did not fall. On a scale of the milliamperemeter cause line, it will correspond to zero value of illumination. Remove paper, the milliamperemeter will show existence of current. Cause the second line of a scale which will correspond to illumination in this point. Using these two points of a scale as basic, create a light meter scale on the basis of the turned-out device which will measure illumination.