Gewiss CHORUS GWA9531, Техническое руководство

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8
LIGHT SENSOR SETTING
8.1 Reflection Factor
An occupancy detector includes a light sensor to measure brightness. Since the detector is
mounted on the room ceiling, it measures the light there too. This means that it measures
light which is present in the room (as sunlight and artificial light) and which is reflected onto
the ceiling. However, not all the light is reflected, as the reflection factor depends heavily on
the surfaces and furnishings. The light value measured on the ceiling does not therefore
represent the room brightness. Therefore, the reflection factor must be determined, and the
KNX occupancy detector adjusted to local conditions.
To determine the reflection factor, please proceed as follows:
1. Switch on the lighting. For fluorescent lamps, it is advisable to let them warm up for
at least 10 minutes, so that they reach their maximum brightness.
2. Place a lux meter in the location where the desired lux value should be achieved,
e.g. at a workstation, and measure the lux value.
3. Determine the brightness at the ceiling, i.e. at the occupancy detector. Hold the lux
meter at the occupancy detector’s location.
The relationship between the brightness measured at the ceiling and the brightness
measured at the workstation represents the reflection factor.
Example:
Measured value, ceiling 300 lux
Measured value, desk 600 lux
This gives a ratio of 1:2, so a reflection factor of 1/2 must be set.
It should be noted that in practice, because of fluctuations in daylight (passing clouds),
documents on desks (white or dark sheets of paper), or the setting of window blinds for
example, the reflection factor continually changes, so that there can be deviations from the
desired/installed set value
.