Chapter 3 __________________________________________________ Installation
VAISALA__________________________________________________________17
CHAPTER 3
INSTALLATION
This chapter provides you with information that is intended
to help you install this product.
General Installation and Alignment
LM21 Background Luminance Sensor is mounted on the
Option Support Arm of FS11 Visibility Sensor (see Figure 2
on page 18). LM21 Background Luminance Sensor should
face north on the northern hemisphere and south on the
southern hemisphere. Direct sunlight into the sensor must be
avoided.
LM21 Background Luminance Sensor is normally tilted in
an angle of 20 to 50 degrees referred to horizontal level. A
good practice to choose the tilt angle is to direct the sensor
slightly above the runway lights. The LM21 sensor is
designed for measuring the background, against which
pilots view the runway lights or the runway markings. A
compromise must be made to achieve a measurement as
representative as possible and, on the other hand, to meet
the installation requirements. The LM21 sensor must not
face the runway lights directly but it should view a part of
the scattered light dome seen by the approaching pilot.
Generally, an installation angle of 30° is recommended
when there is no special reason to use a wider angle.
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