To evaluate the amount of rain which has fallen, planimetric
masurements of the area under the recorded trace are
necessary, which is not an accurate and simple procedure.
2.4.23 Snow gauges
For measuring snowfall, gauges are used where the snow is
melted by heating or by mixing with chemical anti-freezers.
There are also rain recorders with heating devices which can
be used for snowfall measurements as well. Heated recorders
should be constructed in such away as to avoid excessive
evaporation when the heating is on.
2.4.24 Wetness detectors
Rain detectors or wetness detectors are used to record
duration of precipitation. Conventional instruments are
similar to hygrographs except that the sensing element - ab bstring - is exposed openly to precipitation. Electrical
sensors will close or open a switch when precipitation is
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