Chapter 4 Installation; Selecting Location - Vaisala PWD22/52 User Manual

Chapter 4 _______________________________________________________________ Installation
CHAPTER 4
INSTALLATION

Selecting Location

VAISALA _______________________________________________________________________ 29
This chapter provides you with information that is intended to help you
install this product.
Finding a suitable site for the Vaisala Present Weather Detector
PWD22/52 is important for getting representative ambient
measurements. The site should represent the general area of interest.
The main requirements for the location of PWD22/52 are as follows:
1. Locate PWD22/52 in such a way that the measurements will be
representative of the surrounding weather conditions.
- The ideal site for PWD22/52 has a minimum clearance of 100 m
from all large buildings and other constructions that generate
heat and obstruct precipitation droplets. Avoid the shade of trees
because the trees may cause changes in the microclimate.
2. The site should be free of obstacles and reflective surfaces
disturbing the optical measurement as well as obvious sources of
contamination.
- It is recommended that there are no obstacles in the line-of-sight
of the transmitter and receiver units (see Figure 7 on page 30). If
the transmitter beam is reflected from obstacles back to the
receiver unit, then the sensor will indicate too low MOR values
because the reflected signal cannot be distinguished from real
scatter signal. Reflections can be detected by rotating the sensor
cross arm. Any reflections will change depending on the cross
arm orientation and the visibility reading will change
accordingly.