# Illuminance calculation

Document Sample

```					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]
Formula in this case is:

Cos 0 = 1
[Example 1]
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]
Formula in this case is:                   Light fittings

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

Luminous flux 1,000lm

300 cd
[Example 2]