User's Guide _______________________________________________________________________
24 ___________________________________________________________________ M211107EN-C
Location and Orientation
The main requirements for the location of FS11P are presented in the
following:
1. The FS11P sensor should be sited in such a way that the
measurements will be representative of the surrounding weather
conditions.
- FS11P should be located at a minimum distance of 100 m from
any large buildings or other constructions that radiate heat and/or
obstruct precipitation droplets. The shade of trees should also be
avoided because trees may cause changes in the microclimate.
2. The site should be free of obstacles and reflective surfaces that will
disturb the optical measurement, as well as obvious sources of
contamination.
- It is recommended that there be no obstacles in the line-of-sight of
the FSM102 and PWD32 transmitter and receiver units (see Figure
2 below). If the transmitter beam is reflected back to the receiver
unit from obstacles, the sensor will indicate too low MOR values
because the reflected signal cannot be distinguished from the real
scatter signal. Harmful reflections can be detected by rotating the
measurement unit. These reflections change depending on the
measurement unit orientation and the visibility reading will change
accordingly.
1001-134
Figure 2 Recommended Location of FS11P with Mast
FSFM250/FSAM250
- The receiver and transmitter optics should not point towards
powerful light sources or, in bright daylight, towards reflective
surfaces such as bodies of water. It is recommended that the
receiver point North in the Northern hemisphere and South in the
Southern hemisphere. (The transmitter and receiver heads can be
identified by first locating the surface temperature probe, which is
closer to the transmitter.) The receiver circuit may become
saturated in bright light, in which case the built-in diagnostics will
indicate a warning.
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