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The high level of intelligence built into LUXMATE systems is based
on accurately measuring the amount of available daylight. Istalled
outside the building, daylight measuring heads developed by
Zumtobel that have proven themselves thousands of times take
a panoramic lighting snapshot. Eight photocells record the position
of the sun as well as direct and indirect light components once
every second. The geographical location of the installation and its
range of sun positions are stored in every installation. All this
information is used to accurately determine the natural lighting
conditions in a particular room.
Zumtobel recommends its Look Out sensor for relatively simple
systems. This indoor sensor measures incident light in the immedi-
ate vicinity of a window. The system is therefore unaffected by
reflections and reflected glare. Another benefit: it is really easy to
combine this sensor with the daylight measuring head.
Look Down sensors are often marketed as standard components
for daylight integration. Nevertheless, they often cause problems in
practical use. Changing surfaces and luminance levels may distort
the computed control value. Direct incident light from free-standing
luminaires, or reflections on reflective surfaces such as window sills
made of metal also interfere with control. In addition, Look Down
sensors are only approved for standard heights because measured
values decrease with increasing height. The use of a Look Down
sensor is therefore only recommended in the case of movable lumi-
naires and low detection heights such as free-standing luminaires,
for instance.
Different systems –
Daylight
Look Out
Look Down
a direct comparison
measuring head
sensor
sensor
Accuracy of measurement results
++
+
-
Susceptibility to lighting effects
++
+
-
Commissioning expense
++
+
+
Design and room vista
++
+
+
Restrictions with regard to installation
++
+
+
Constancy of illumination
++
+
-