Polar Diagram Lf/U 2.1 - ABB i-bus KNX Product Manual

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ABB i-bus KNX
Device technology
2.2.4

Polar diagram LF/U 2.1

The light sensors include two fiber-optic rods. The white fiber-optic rod has a smaller detection range and
is less sensitive to lateral lighting influences. This fiber-optic rod can be used if the detection range has to
be limited as the reflected light may be influenced, for example, by window sills, which affects the large
reference area of the clear fiber-optic rod.
Note
Please note that the white fiber-optic rod may not be subject to direct sunlight, artificial light or
reflections. This leads to a direct misinterpretation of the brightness in the reference area and thus to
incorrect constant lighting control.
The diagrams show the light sensitivity of the sensors in the room. The percentage values refer to the
maximum sensitivity of the LF/U.
2.2.5 Checking the LF/U 2.1
On the Light Controller, a DC voltage of a few mV can be measured directly with a multi-function
measurement device. Disconnect the LF/U from the DLR/A for this purpose. The value is between 0 mV
(absolute darkness) and a few 100 mV depending on the brightness. If 0 mV is also measured at normal
brightness, this is due to an open circuit, short circuit or a defective LF/U.
22 2CDC507128D0202 | DLR/A 4.8.1.1