Tipping Bucket

ASOS uses a heated tipping bucket rain gauge, such as the Frise Model 7405HA, as its standard sensor for measuring liquid precipitation accumulation. This instrument operates on a simple yet effective principle: a small, precisely balanced bucket is designed to tip over when it collects a specific amount of precipitation (typically 0.01 inch). Each tip is then electronically recorded, providing a cumulative measure of rainfall over time. To ensure year-round operation in various climates, the Frise tipping bucket is heated, allowing it to melt frozen precipitation like snow and freezing rain, converting it into a liquid equivalent for measurement. While this design has been a workhorse for automated weather observations, efforts have continuously been made to improve its performance, especially in challenging conditions, with the eventual aim of replacing it with more advanced all-weather precipitation accumulation gauges (AWPAGs) that offer enhanced accuracy across all precipitation types.