How a Tipping Bucket Rain Gauge Works

A see-saw and a magnet

Rain runs off a funnel of known area into a small plastic see-saw with two chambers. When one side fills, it tips, empties, and brings the other side up. A magnet on the see-saw passes a reed switch on each tip, and the electronics count tips. Each tip equals a fixed depth of rain over the funnel area — on our gauges the resolution is 0.3 mm below 1,000 mm of total accumulation and 1 mm above it.

Rate versus accumulation

From those counts the console derives two different things. Rate is tips per unit time converted to mm/h, and it moves fast. Accumulation is the running total over 24 hours, a week, a month, and since reset. Buyers tend to care about accumulation; growers deciding whether to irrigate care about both, because 20 mm over an hour and 20 mm over a day do very different things to a field.

Where the error comes from

A tipping bucket under-reads in very heavy rain, because water keeps arriving while the bucket is mid-tip. Our published accuracy reflects this: within ±1 mm below 15 mm, and ±7% from 15 mm up to 9,999 mm. Any gauge that claims a flat percentage across all intensities is quoting a marketing figure rather than a measured one.

Installation decides the reading

The funnel needs open sky. Mounted under a tree, beside a wall or below a roof edge, the gauge measures the building and not the weather. It also needs to be level — a tilted see-saw tips early on one side and late on the other. And it needs cleaning: leaves, insects and dust in the funnel are the most common cause of a gauge that has stopped counting.