TOBIAS GRAU XT-S Notice D'utilisation page 8

Functions description of the constant light regulator
The function of the Constant Light Regulator ensures that the luminaire regulates itself according to the
ambient light level. This ensures not only a constant light level, but also that only as much energy is used as
is actually needed. Savings of approximately 50% energy consumption are possible here when compared to
purely 'on/off switching' lighting systems.
The sensor has a built-in photocell in order to detect whether the brightness level changes in the room or
on the surface below the luminaire. This photocell measures the light intensity that is reflected back from
an area below the luminaire. If the photocell measures a low level of light, the luminaire will dim up - if more
light is measured, the luminaire dims down.
At delivery, the photocell is set to produce an
luminance of approximately 500-600lx from
a reflective surface underneath the luminaire
at a reflective angle of about 30%.
As the luminaire at delivery is primarily dependant on
the light intensity measured by photocell, it may be that
dark areas below the luminaire (e.g. a dark floor) or very
bright areas (e.g. a luminaire that sits very close to a window,
whereby the area underneath the luminaire reflects a lot of
light onto the photocell and also a lot of light passes through
the window itself and enters the photocell) can create a perceived
"malfunction" of the luminaire.
Example 1:
Luminaire stands on a black carpet and always dims down very strongly. It has a new saved light level, but
this has not led to an improvement.
Explanation: Since the floor reflects hardly any light, there is also not a lot of light being measured by the
photocell at a highly dimmed light.
Solution: Set the desired luminance and hold a white DIN A4 sheet about 30cm below the sensor when
saving this value (see description mode, Mode 5). Important: the paper must be held in this position during
the 10 second calibration time!
Example 2:
The luminaire stands at the window and always dims down very strongly. It has saved a new light level, but
this has not led to an improvement.
Explanation: Since a lot of light passes directly through the window (even in cloudy weather), and not only
from the reflection of the surface below the luminaire to the photocell, the difference in light intensity mea-
sured by the photocell is too low.
Solution: Set the desired luminance and hold a white DIN A4 sheet about 30cm below the sensor when
saving this value (see description mode, Mode 5). Important: the paper must be held in this position during
the 10 second calibration time!
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