Rain Gauge, an instrument used to measure precipitation. Rain is measured directly; snow, hail, and sleet must first be melted. Approximately 10 inches of snow equal one inch of rain, but this figure varies with the compactness of the snow.
A standard rain gauge consists of a funnel leading to a measuring tube. The area of the circular top of the funnel is 10 times that of the tube's cross section, so that one inch of water falling on the funnel will rise to 10 inches in the tube. The tube thus multiplies the height of the fallen water by 10, making it possible to measure small amounts of precipitation.
A tipping bucket rain gauge contains a small bucket mounted on a pivot. The bucket is divided into two compartments. When one compartment receives 1100 inch (or, for metric gauges, 0.2 mm) of rain or meltwater, the bucket tips, dumping the water. The other compartment then receives the precipitation. Each time the bucket tips, an electric circuit is closed and a mark is recorded on moving paper. The marks show how much precipitation has fallen and the rate of fall.
A weighing-type rain gauge weighs the precipitation as it falls into a container resting on a scale and records the weight, usually on revolving graph paper.