The ordinary rain-gauge consists of :
- An upper section which is a cylindrical portion with an accurately turned and bevelled rim, within which is attached a funnel.
- An outer case with a splayed base.
- A cylindrical collecting can fitted with a wire handle.
The upper section fits closely on top of the outer case, the tube of the funnel fitting inside a plastic bottle placed in the collecting can. The upper section and collecting can are made from seamless drawn copper tubing, but the remainder of the gauge, apart from the brass fittings and the bottle, is made from sheet copper with soldered seams. The use of copper tubing in the construction of the cylindrical portion ensures the interchangeability of the funnels among different gauges. The brass rim has a diameter of 8 inches (203-mm) in the tropical region and the cylindrical portion is over 4 inches deep to minimize the amount of rain lost by out-splashing from the sides of the funnel. The rain is collected in the plastic bottle or exceptionally it may flow into the collecting can. Rainfall is measured by pouring the collected water into a separate measuring jar or cylinder.