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| Lamp capacity, Wt | Voltage, V | |
| 110, 120, 127 | ||
| less than 110 | 2.4 | 2.0 |
| 110 and more | 3.2 | 2.5 |
Illuminance determination using the luxmeter.
The determination of horizontal illuminance at the workplace is done with the help of luxmeter (see topic 4, appendix 2). The 0.9 correction coefficient is used for the luminescent lamps of day illumination (LD); 1.1 - for the white lamps; 1.2 - for the mercury-discharge lamps, because the device has initially been intended for measuring of the illuminance, produced by incandescent lamps.
If the determination is done in the morning or in the afternoon, it’s necessary to determine the illuminance, produced by the mixed illumination (both natural and artificial). After that the determination is done when the artificial illumination is switched off. The difference between the received data is the value of illuminance, produced by the artificial illumination.
The illumination evenness is determined by the “Envelope method,” which means that illuminance is measured at 5 different points of the premises and evaluated by calculation of illuminance variety coefficient (minimum illuminance divided by the maximum illuminance at two different points, which are 0.75 m from each other, when the evenness is determined at the workplace, or 5 m from each other, if the evenness is determined in the whole room).
The calculation of the workplane brightness is made using to the formula:
where, B - is brightness, cd/m2;
E - illumination, lux;
C - coefficient of surface reflection
(0.7 - white; 0.5 - light-beige; 0.4 -brown; 0.1 - black).
The allowable brightness of general illumination lamps for residential and public premises is given in the table 4.
Table 4
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