ABB i-bus KNX Product Manual page 94


ABB i-bus KNX
Commissioning

No: The dimming curve is not modified. The DALI dimming curve as it is stipulated in the DALI
standard (EN 62386 and EN 60929) is used unchanged for the control of DALI devices.
For further information see:

Yes: linear lighting curve: The KNX value range is converted to the DALI value range so that a linear
relationship between KNX values and DALI values (electronic power on the lighting equipment or
luminous flux) results. The logarithmic DALI characteristic curve is thus converted to a linear
representation. In this way, ballasts with an applied minimum dimming value (in other words luminous
flux) of 3 % can be controlled exactly with this value. Should the logarithmic DALI characteristic curve
be applied, the KNX value of 50 % would be applied in this case.
For further information see:

Yes: linear light.curve, without phys-min bright.: The KNX value range (1...255) is converted to the
DALI value range (physical minimum...254) whereby the unusable range of DALI control values
(0...physical minimum) which the lighting equipment cannot realize is omitted.
For further information see:
Note
Characteristic adjustment can only be performed correctly when the brightness value is internally
calculated and simulated with the characteristic adjustment via the DALI Light Controller and transferred
to the DALI devices. This is the case when the brightness value is set, for example.
During dimming, irrespective of whether a group command or central command is concerned,
differences may occur between the set brightness value and the (simulated) status of the brightness
value. To allow even dimming, the DALI Light Controller must use the DALI commands DIM-UP and
DIM-DOWN. These commands trigger a dim step in the DALI device, which is transformed using the
DALI characteristic stored in the DALI device. As the exact length of the dim step is not known, there
may be deviations between the calculated (simulated) value and the brightness value actually set.
This can occur when, after dimming, the status of the brightness value is fed back to the dimmed
lighting group as a brightness value. In this case, there may be a brightness jump.
92 2CDC 507 100 D0202 | DLR/S 8.16.1M
DALI dimming curve, page 195
DALI dimming curve, page 195
DALI dimming curve, page 195