How brightly surfaces in workplaces, warehouses, halls and other places where people are present are illuminated is extremely important. It makes seeing and doing certain activities comfortable and safe for us, so it is advisable to ensure the proper light intensity. To this end, standards are helpful, including PN-EN 12464-1, which includes the recommended values of intensity in selected areas.
Basic principles of lminous intensity measurements
The device used to perform luminous intensity measurements is a lux meter, also known asa photometer. It is designed to measure the luminous intenstity expressed in lux (lx) on a work surface. Measurements with a lux meter should be taken under the environmental conditions, particularly the temperature and humidity, specified by the manufacturer.
Luminous intensity values depend on the type of premises and the work performed there. The higher the precision of the work performed, the higher the intensity should be. For example, for general lighting in warehouses, it is recommended that the average luminous intenstity should be between 100 lx and 200 lx, while for precision assembly workplaces this value should be at least 750 lx.
When carrying out tests, it is necessary to verify the existing light sources: type, number, power output and possible degree of soiling. Note also that discharge lamps should be switched on at least 30 minutes beforehand, and the measurements themselves should be carried out while the system is in operation and with no access by daylight.
How to perform luminous intensity measurements?
It is worth noting that luminous intensity is affected by a number of factors. These certinly include the efficiency of the light source, but also the surrounding elements, such as the colours and materials of the walls and furniture. If the reflectance values of these surfaces are unknown they should also be determined in the luminous intensity measurement.
The measurements must be based on a measuring grid and the way it has been prepared should be reflected in the measurement report. The luinous intenstiy test should be carried out on a plane at the work place and in its immediate vicinity. Luminous intensity measurements must be done at all points on the grid.
Luminous intensity measurements – who performs them and when?
Lighting installers or upgrade contractors should have a person in their team responsible for luminous intensity measurements. When replacing an inefficient lighting system, the measurements are carried out during the operation of the existing system, and then the newly installed luminaires as well. It is recommended that the person carrying out the measurements should wear dark clothing. This is important in order to minimise light reflections. Luminous intensity measurements at workplaces should be performed every 2 years or whenever the use or layout of the area concerned has changed.
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