ideal shape

The ARG-100 Aerodynamic Rain Gauge was designed by the Institute of Hydrology, Wallingford, UK with a profile very similar to that derived by the UK Meteorological office as an 'ideal' shape.

Research has shown that a conventionally shaped raingauge interferes with the airflow and that the flow accelerates and turbulence increases over the top of the funnel than otherwise would have fallen on the ground.

The ARG-100 Aerodynamic Rain Gauge has been designed to minimize the above effect by presenting a reduced area to the wind. The body of the ARG-100 has a profile which has been designed to reduce drag and turbulence and therefore be sited conventionally on exposed sites with some confidence.

The unique aerodynamic shape of the ARG-100 typically captures at least 5% more rainfall than most traditionally-shaped cylindrical gauges.

features

• ideal shape — designed by the Institute of Hydrology, Wallingford, UK
• designed to minimize interference with airflow by presenting a reduced area to the wind
• typically captures at least 5% more rainfall than most traditionally-shaped cylindrical gauges
• manufactured in U.V.-resistant plastic by vacuum-forming techniques
• low cost
• rugged instrument of comparable precision to gauges fabricated in other materials
• rainfall is measured by the well-proven tipping bucket method
• compatible with all loggers or event recorders

ARG-100 SPECIFICATIONS
Funnel Diameter	254mm (10.0 inches)
Funnel Rim Height	340mm (13.4 inches)
Tip Sensitivity	Standard setting 0.20mm of rain per tip; other setting 0.25mm, if required.
Output	Contact closure
Power Requirements	N/A
Maximum Allowable Current Through Reed	300 mA; non inductive
Weight	1000 gms

tipping bucket method

Rainfall is measured by the well-proven tipping bucket method. Precipitation is collected by a the funnel and is passed to one of the two buckets situated at either end of a short balance arm. The balance arm tips when the first bucket is full, emptying this bucket and positioning the second bucket under the funnel. The tipping process repeats indefinitely as long as the rain continues to fall, with each tip corresponding to a fixed quantity of rainfall; at each tip the moving arm forces a magnet past a reed switch, causing contact to be made for a few milliseconds.

The tipping bucket method provides a contact closure at each tip. This is compatible with all loggers or event recorders. If required, Waterra can also supply a small data logger which fits in a recess within the body of the gauge.

The pulses returned during rainfall may be counted over any time interval desired, allowing accurate determination of the rainfall rate (this variable some times called intensity, is frequently used in soil erosion studies and is relevant to some aspects of crop pathology).