Med-Hycos - the Data
The principle of this type of recording gauge is very simple. A light metal container id divided into two compartments and is balanced in unstable equilibrium about a horizontal axis. The rain is led from a conventional collecting funnel into the uppermost compartment. As for the raingauge, the size of the opening of the collector is not really important, but a standard area of about 400cm² should probably found convenient.
The main advantage of this type
of instrument is that it can have an electronic pulse output and can be
recorded at a distance or for simultaneous recording of rainfall and river
stage on a water stage recorder.
After a predetermined amount of
rain has fallen, the bucket became unstable in its present position and
tips over to its other position of rest. The compartments of the container
are so shaped that the water can now flow out of the lower one and leave
it empty. Meanwhile, the rain falls into the newly positioned upper compartment.
The movement of the bucket, as it tips over, is used to operate a relay
contact and produce a record that consists of discontinuous steps. The
distance between each step represents the time taken for a pre6specified
amount of rain to fall. For many hydrological purposes, in particular for
heavy rainfall areas and flood warning systems, 0.5 to 1.0 millimetre buckets
CONDITIONS OF USE
All gauges in any area or country should have comparable exposures, and the same siting criteria should be applied to all. The gauge should be exposed with its orifice being horizontal over ground level. The height of the gauge orifice above the ground should be as low as possible because the wind velocity increases with height, but it should be high enough to prevent splash from the ground. A standard height of one metre is recommended.
When adequate conditions from the
wind is not possible, individual objects should not be closer to the gauge
than a distance equal to four times their height.
Ring collector with a sharp edge
linked to a cone-shaped funnel with a sufficient slope to avoid splashing