A tipping bucket rain gauge records rainfall by counting the tips of a small see-saw bucket that empties each time it fills with a fixed depth of rain.
A tipping bucket rain gauge measures rainfall by funnelling rain into a small two-sided bucket that tips each time it fills with a fixed amount. Each tip closes a switch, usually a reed switch worked by a magnet, and a data logger counts the tips. The bucket sits on a pivot like a see-saw. When one side fills, it tips over, empties, and brings the other side under the funnel. Each tip equals a set depth of rain, often 0.2 mm, though some gauges use 0.1 mm or 0.5 mm. Rainfall is the number of tips times the tip depth, and rainfall intensity comes from the time between tips. These gauges are standard at automatic weather stations, flood warning networks, urban drainage studies and any site where rainfall is sent in near real time by telemetry. They show when rain fell, which a daily manual gauge cannot. The main error is under-catch in heavy rain. While the bucket is tipping, rain keeps falling in and is lost, so the gauge reads low at high intensity. The error grows with intensity and can be reduced with dynamic calibration or a correction curve. Wind also carries drops past the funnel, so gauges on exposed sites read low, as do all rain gauges. In light rain, water in a part-filled bucket may evaporate before it tips. A plain tipping bucket does not measure snow unless heated. Leaves, insects and dust can block the funnel or filter, so clean it on each visit. Calibrate by pouring a known volume in slowly and counting tips. Keep the gauge level and away from trees and buildings. For example, a gauge with 0.2 mm buckets that records 45 tips in 30 minutes shows 9.0 mm of rain, an average intensity of 18 mm/h. Strengths are low cost, low power and fine time detail. Limits are under-catch at high intensity and the need for regular cleaning and calibration.