ABB i-bus KNX Product Manual page 174

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ABB i-bus KNX
Planning and application
Light control constraints
Rooms are lit up differently by the incidental daylight and the artificial light 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 light 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, people,
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
Lighting equipment with varying brightness characteristic curves should be avoided in control circuits. In
a DALI Light Controller circuit, a mix of DALI lighting equipment and 1-10 V lighting equipment
(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 lighting equipment, causes a brightness of 50 %. With DALI
lighting equipment, 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.
172 2CDC 507 100 D0202 | DLR/S 8.16.1M