ABB i-bus KNX Product Manual page 170

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ABB i-bus KNX
Planning and application
Lighting control constraints
Rooms are lit up differently by the incidental daylight and the artificial lighting of the lamps. Not all surfaces
in the rooms, e.g. walls, floor and furniture reflect the light, which falls on them, in the same manner.
Accordingly, even though there is an exactly calibrated constant lighting control in daily operation,
deviations to the set target value may occur. These deviations may be up to +/- 100 lx should the current
ambient conditions in the room, and accordingly the reflection properties of the surfaces (paper, persons,
reorganized or new furniture), differ significantly from the original ambient conditions at the time of
calibration.
Deviations may also occur if the light sensor is influenced by direct or reflected light falling on it, which is
not influenced or only slightly influenced by the surfaces in the detection range of the light sensor.
Note
Luminaires with varying brightness characteristic curves should be avoided in control circuits. In a DALI
Light Controller circuit, a mix of DALI luminaires and 1-10 V luminaires (controlled via Switch/Dim
Actuator SD/S) is not possible.
This is because of the different brightness characteristic curves (linear/logarithmic) involved. The same
control value, e.g. of 50 % with 1-10 V luminaires causes a brightness of 50 %. Using DALI luminaires,
where the characteristic curve is adapted logarithmically to the response of the human eye, a light
current of 3 % results in a brightness level of about 3 %.
Because of these brightness differences at the same control value, a common lighting control (in a DALI
Light Controller control circuit) is not possible.
168 2CDC507128D0202 | DLR/A 4.8.1.1