Casella CEL Piche evaporimeter - Manual (Page 4)

Hb3127-02
4
Invert the tube and hang up on the stand. Wait a few minutes until the disc is
thoroughly moist and the flow of air bubbles up the tube has practically ceased.
Read the water level and record it alongside the other meteorological data.
At the next observing hour, or more commonly 24 hours later, observe the new
water level reading. If the level is less than half way remove the evaporimeter and
refill the tube. If the paper disc is damaged or is covered with sand or dust, remove
it.
The rate of evaporation is usually expressed as the volume of water evaporated per
unit area in unit time.
The outside diameter of the tube is the same as the metal disk; the diameter of the
paper disc is 3.0cm. Since both surfaces of the disk contribute to the evaporation
the free surface area is 11sq cm.
There are a number of ways in which evaporation figures can be used, but owing to
the large influence of wind, exposure and dry bulb temperature no one formula is
applicable to relate Piche readings to free water or ground evaporation.
The Piche evaporimeter is a simple and inexpensive instrument, which provides a
valuable index of evaporation. It can be used to provide a useful comparison
between similar places. Whilst it may be possible to relate the evaporation figures
from a Piche evaporimeter to those from a natural surface, a different relationship
may be expected for each type of surface and for different climates.
SERVICE
Casella’s in house service department offers a comprehensive range of repair and
calibration services, designed to effect a fast and efficient back up for all our
products. The service department is operated under the scope of our BSI
registration for products manufactured by us. We will however, undertake the
repair of other manufactures equipment.
For further information please contact our service department at our Bedford
headquarters. We will be happy to provide quotations for individual repairs or
provide annual maintenance under contract.
SPARE PARTS
M112067
Piche Evaporimeter with disc retaining clip and 400 discs
B7215/3 Stand for suspending instrument
A7215/1 Disc retaining clip
M112069 Pack of 400 paper discs