Chapter 4 Installation; Selecting Location - Vaisala PWD22 User Manual

Chapter 4_________________________________________________________________ Installation
CHAPTER 4
INSTALLATION

Selecting Location

VAISALA ________________________________________________________________________ 37
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 is important for getting representative ambient measurements.
The site should represent the general area of interest.
The main requirements for the location of PWD22 are as follows:
1. Locate PWD22 in such a way that the measurements will be
representative of the surrounding weather conditions.
- The ideal site for PWD22 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 9 on
page 38). 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 crossarm. Any reflections will
change depending on the crossarm orientation and the
visibility reading will change accordingly.