Casella CEL Piche evaporimeter - Manual (Page 3)

Hb3127-02
3
GENERAL APPLICATION
The Piche evaporimeter is a type of Atometer used to measure the rate of
evaporation from a wet disc of absorbent paper. It is used mainly in hot, dry
climates where water loss through evaporation must be observed regularly. Since
the results are dependent on wind speed past the disc, as well as the wet bulb
saturation deficit, it is almost essential to expose the evaporimeter inside a
meteorological screen.
CONSTRUCTION
A glass tube graduated in steps of 0.1ml will contain just
over 30m l of water. A m etal clip holds the paper disk
against the open end, while a ring at the closed end
allows the tube to be hung vertically.
INSTALLATION
The evaporimeter is best suspended from a stand
available from Casella or from a hook fixed to the roof of
a meteorological screen.
Piche evaporimeter hanging from a stand.
DAILY USE
Hold the tube vertical, closed end downwards, and fill completely with clean
distilled water. Slide the clip over the end and rotate it until the disc is central with
the tube but not quite touching it. With clean, grease-free, fingers or tweezers if
available, insert a new disc between the tube and the clip. Push down the clip to
grip the paper firmly. It is recommended for even wetting of the disk that a pinhole
should be made in the centre of the paper disk through the metal disk.