Illumination_Environment-_2010

Illumination_Environment-_2010 - Associate Professor Dr...

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Unformatted text preview: Associate Professor Dr Siti Zawiah Md Dawal Dept. of Engineering Design and Manufacture Faculty of engineering University of Malaya 1 Ergonomics Workstation 2 3 ILLUMINATION The basic theory applies to a point source of light (such as a candle) of a given luminous intensity, measured in candelas (cd) Light emanates spherically in all directions from the source. The amount of light striking a surface, or a section of this sphere, is termed illumination or illuminance and is measured in foot-candles (fc). The amount of illumination striking a surface drops off as the square of the distance (d) in feet from the source to the surface: illuminance = intensity/d 2 4 Some of that light is absorbed and some of it is reflected (for translucent materials, some is also transmitted), which allows humans to "see" that object and provides a perception of brightness. The amount reflected is termed luminance and is measured infoot-lamberts (fL). It is determined by the reflective properties of the surface, known as reflectance: luminance = illuminance X reflectance 5 Illustration of the distribution of light source following the inverse-square law 6 ILLUMINANCE Recognizing the complexity of extending the point source theory to real light sources (which can be anything but a point source) and some of the uncertainties and constraints of Blackwell's (1959) laboratory setting, the IESNA adopted a much simpler approach for determining minimum levels of illumination (IESNA, 1995). 7 8 Recommended Illumination Levels for Use in Interior Lighting Design The first step is to identify the general type of activity to be performed and classify it into one of nine categories, shown in Table 6-2. A more extensive list of specific tasks for this process can be found in IESNA (1995). Note that categories A, B, and C do not involve specific visual tasks. For each category, there is a range of illuminances (low, middle, high). The appropriate value is selected by calculating a weighting factor....
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This note was uploaded on 01/06/2011 for the course MANUFACTUR KXGP6103 taught by Professor Siti during the Summer '10 term at University of Malaya.

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Illumination_Environment-_2010 - Associate Professor Dr...

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