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Illuminance calculation

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					Illuminance Calculation
Introduction (Key word)
1. Luminous Flux      Unit : lm (lumen)

  Quantity of light

[Exmaple] Fluorescent lamp
Introduction (Key word)
2. Luminous intensity         Unit : cd (candela)

  Light intensity
[Exmaple] A certain light fittings (HID)
Distribution Curve of Luminous intensity

                           [Example] Batten type




    cd / 1000lm
Illuminance Calculation
Direct illuminance by a point source of light
Direct horizontal illuminance Eh in the point P on a certain plane
by a point source of light L is:




       Luminous intensity
       of the direction of  (cd)
       Distance from light source
       to the point (Unit: m)

       Incident angle
[Example 1]
   Calculate the illuminance of directly below P0 when
   one light fittings HAYBAY that has the distribution
   curve of luminous intensity as shown below is set on
   the ceiling (height:7 m) with using Metal Halide lamp
   400W (MF400 L/BU-P)?

            Distribution curve of Luminous intensity
                   (Luminous flux is 1,000 lm)
[Example 1]
Answer
 Formula in this case is:



     Cos 0 = 1
[Example 1]
Answer
 According to the distribution curve of
 luminous intensity curve, I of the
 beneath direction is 540 cd. However,
 since it is written as luminous flux
 1,000 lm, we have to multiply 30.5.
 * Luminous flux of MF400 L/BU-P is       Luminous flux 1,000lm
 30,500 lm




                                                         540 cd
 Therefore, illuminance of beneath
 becomes:
[Example 2]

  Calculate the horizontal illuminance of P5 that is away
  by 5m from the P0?




                           Light fittings
[Example 2]
Answer
 Formula in this case is:                   Light fittings




  From the distribution curve of
  luminous intensity , I is:

                                   Luminous flux 1,000lm




                                                             300 cd
[Example 2]
Answer

 Therefore, illuminance of P5
 becomes:

				
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posted:12/9/2010
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