A tipping bucket rain gauge is a precipitation sensor that measures rainfall by funneling water into a small seesaw with two opposing buckets that tip alternately when each bucket fills to a fixed volume. The Davis Instruments 7852 and the standard NWS HO-83 ASOS sensor both use this mechanism. Each tip closes a reed switch and registers a discrete pulse — typically 0.2 mm or 0.01 inch of rain. That pulse train is what gives hydrologists and weather services rainfall depth and intensity in real time.
Tipping Bucket Rain Gauge Interactive Calculator
Vary tip count, bucket calibration, logging interval, and catch area to see rainfall depth, intensity, bucket volume, and pulse rate.
Equation Used
The gauge converts rainfall into counted pulses. Total depth is the number of bucket tips multiplied by the calibrated depth per tip. Intensity is that same depth divided by the logging interval. Bucket volume is estimated from catch area using 1 mm over 1 cm2 = 0.1 mL.
- Each reed-switch pulse equals one completed bucket tip.
- The calibrated depth per tip is constant over the interval.
- Catch area is level and unobstructed.
- Dynamic high-intensity under-catch correction is not included.
Operating Principle of the Tipping Bucket Rain Gauge
Rain falls into a collector funnel of a precisely known catch area — usually 200 cm² or 8 inches diameter — and gets channelled down onto one side of a balanced seesaw. The seesaw carries two small buckets back-to-back. One bucket sits under the funnel outlet collecting water, the other sits empty on the opposite side of the pivot. When the filling bucket reaches its calibrated volume, the centre of mass crosses the pivot axis and the assembly tips fast under gravity, dumping that bucket and bringing the empty one into the catch position. A small magnet on the seesaw passes a reed switch on each tip, and the data logger counts pulses.
The whole device is a mechanical analog-to-digital converter. Continuous rainfall becomes discrete pulses, and each pulse equals one calibrated unit of precipitation. The geometry has to be right — the bucket volume, the catch area, and the pivot friction all interact. If the pivot bushings drag, the seesaw tips late and you over-read each bucket. If the buckets are bent or the gauge is out of level by more than 1°, one side tips faster than the other and your rainfall depth skews. You will see this as alternating-tip asymmetry on the data log.
The well-known weakness is high rainfall intensity. During the fraction of a second the seesaw is mid-tip, water keeps falling into a moving bucket and some splashes out. Above roughly 50 mm/h the under-catch becomes measurable — typically 5-15% by 100 mm/h depending on the design. Manufacturers like OTT HydroMet and Texas Electronics publish dynamic correction curves to compensate. The other failure mode is debris — a single pine needle across the funnel screen will block flow entirely and your station will report zero rainfall through a thunderstorm.
Key Components
- Collector Funnel: Captures rainfall over a defined catch area, typically 200 cm² or a 203 mm (8 in) diameter aperture matching WMO guidance. The rim must be sharp-edged and level — a rolled or burred rim deflects droplets and changes effective catch area by 1-3%.
- Tipping Seesaw: Two buckets joined back-to-back on a low-friction pivot, balanced so that a calibrated water mass tips the assembly. Bucket volume is set to deliver 0.1, 0.2, 0.5 or 1.0 mm per tip depending on resolution class. The stops that limit travel must be symmetric within 0.5 mm or one side tips at a different fill level.
- Pivot Bearings: Usually jewelled or stainless pin-in-bushing pairs. Friction has to stay below roughly 0.05 N·mm of breakaway torque, otherwise low-rate drizzle accumulates extra mass before tipping and the gauge over-reads in light rain. A common service issue is corrosion film on a brass pivot pin in coastal stations.
- Reed Switch and Magnet: A small NdFeB magnet on the seesaw arm sweeps past a hermetically sealed reed switch on every tip. Switch life is 10⁸ operations typical, which at 0.2 mm/tip survives well over 200 m of cumulative rainfall. Bounce of 1-2 ms is normal — the logger debounces in firmware.
- Drain Mesh and Outlet: A coarse stainless screen at the funnel throat blocks insects, leaves and pine needles. Mesh aperture is usually 0.5-1.0 mm. Smaller than that clogs with pollen; larger lets bug bodies through to the bucket where they bias the tip mass.
- Levelling Base: Three adjustable feet and a bullseye spirit level. Out-of-level above 1° gives systematic asymmetric tipping and a measurable bias between the two buckets that shows up as alternating short/long inter-tip intervals during steady rain.
Industries That Rely on the Tipping Bucket Rain Gauge
Anywhere precipitation depth and intensity matter and the data has to log automatically, the tipping bucket rain gauge is the default. It is mechanically simple, draws zero idle power between tips, and produces a pulse train that any logger can count — from a $30 hobby ESP32 board to a national meteorological network.
- National Meteorology: The U.S. NWS ASOS network uses heated tipping bucket rain gauges at thousands of airport weather stations for METAR rainfall reporting.
- Hydrology and Flood Warning: USGS streamflow stations pair a tipping bucket gauge — often a Texas Electronics TE525 — with stream-stage sensors to drive flash flood guidance for the National Weather Service.
- Agriculture: Davis Instruments Vantage Pro2 stations on vineyards in Napa and Marlborough log rainfall through a tipping bucket to time irrigation and frost protection.
- Urban Stormwater: Melbourne Water and Sydney Water deploy OTT Pluvio² and tipping bucket networks across their catchments to calibrate stormwater hydraulic models.
- Research and Education: University of Reading and NCAR field campaigns use tipping bucket arrays alongside disdrometers to study rainfall spatial variability at sub-kilometre scales.
- Hobbyist and Citizen Science: The CWOP and Weather Underground networks run tens of thousands of consumer Acu-Rite, Ambient Weather and Davis tipping bucket gauges feeding into NOAA's MADIS data stream.
The Formula Behind the Tipping Bucket Rain Gauge
The core relationship converts a tip count over a known interval into rainfall depth and intensity. The interesting numbers are not at the nominal middle — they are at the edges of the operating range. At drizzle rates of 1-2 mm/h, a 0.2 mm gauge tips only every 6-12 minutes and your intensity estimate is coarse. At cloudburst rates above 100 mm/h the seesaw is tipping every couple of seconds and water loss during the tip itself becomes the dominant error. The sweet spot is roughly 5-50 mm/h where tip count is high enough for good time resolution but mid-tip splash loss stays under 2%.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| R | Total rainfall depth over the interval | mm | in |
| N | Number of tips counted in the interval | count | count |
| Vtip | Calibrated rainfall depth per tip | mm/tip | in/tip |
| I | Rainfall intensity over the interval | mm/h | in/h |
| Δt | Interval duration | h | h |
Worked Example: Tipping Bucket Rain Gauge in a vineyard weather station in Marlborough
A vineyard manager in Marlborough, New Zealand runs a Davis Vantage Pro2 with a 0.2 mm tipping bucket gauge feeding a Davis ISS console. During a frontal passage on a Tuesday afternoon the logger records 47 tips in 30 minutes. The manager wants to know rainfall depth, intensity, and whether the value is trustworthy given the gauge has not been calibrated in 18 months.
Given
- Vtip = 0.2 mm/tip
- N = 47 tips
- Δt = 0.5 h
Solution
Step 1 — at the nominal count of 47 tips, total rainfall depth is:
Step 2 — convert to intensity over the 30 minute interval:
That sits squarely in the gauge's accurate range — splash loss at 18.8 mm/h is well under 1% and the manager can trust the depth to roughly ±2%, which is the typical Davis factory spec.
Step 3 — at the low end of the typical operating range, imagine the same front had delivered drizzle and produced only 5 tips in 30 minutes:
That is light rain you would barely hear on the cab roof. The depth is fine but the timing of each tip carries a quantisation error of roughly ±5% because tips are spaced 6 minutes apart — you cannot resolve sub-6-minute variation in intensity.
Step 4 — at the high end, a tropical-style cloudburst delivering 250 tips in the same 30 minutes:
That number is theoretical. In practice a 0.2 mm gauge under-catches by 8-12% at 100 mm/h because water keeps falling into the bucket during the tip motion. The manager would need to apply a manufacturer's dynamic correction curve, or expect the true intensity to be closer to 110-115 mm/h.
Result
Nominal rainfall is 9. 4 mm in 30 minutes, an intensity of 18.8 mm/h. That is steady moderate rain — the kind that soaks a vineyard row in one pass and runs off compacted tractor lanes. At the 2.0 mm/h drizzle end the gauge resolves depth fine but timing is coarse, and at the 100 mm/h cloudburst end raw counts under-read true rainfall by roughly 10% before correction. If a measured total looks low compared with a neighbouring station, the most likely causes are: (1) partial funnel blockage from leaves or insect debris dropping the effective catch area, (2) a gauge tilted more than 1° causing one bucket to tip at a different fill level than its partner — visible as alternating long/short inter-tip intervals on the log, or (3) a worn pivot showing breakaway torque above 0.05 N·mm so light rain accumulates extra water before each tip and very light events go uncounted entirely.
Tipping Bucket Rain Gauge vs Alternatives
The tipping bucket is the workhorse but it is not the only option. Weighing gauges and optical disdrometers compete for the same role at different price and accuracy points.
| Property | Tipping Bucket Rain Gauge | Weighing Rain Gauge (e.g. OTT Pluvio²) | Optical Disdrometer (e.g. OTT Parsivel²) |
|---|---|---|---|
| Resolution per measurement | 0.1-1.0 mm per tip | 0.01-0.05 mm continuous | Drop-by-drop, derives intensity to 0.001 mm/h |
| Accuracy at 20 mm/h | ±2-3% | ±0.1 mm or ±1% | ±5% (uses fall-velocity model) |
| Accuracy at 100 mm/h | −8 to −15% before correction | ±1% | ±5-10% |
| Typical purchase cost (USD) | $80-$800 | $3,000-$8,000 | $5,000-$15,000 |
| Power draw between events | 0 W (passive reed switch) | 1-3 W (load cell + electronics) | 3-5 W (laser + processor) |
| Snow / mixed precipitation | Poor without heated funnel | Excellent with antifreeze | Good — classifies hydrometeor type |
| Service interval | Annual clean and calibration | 2-3 years, refill antifreeze | Annual laser window clean |
| Common failure mode | Funnel blockage, pivot wear | Load cell drift, evaporation loss | Dirty laser optics, spider webs |
Frequently Asked Questions About Tipping Bucket Rain Gauge
The most common cause is wetting and evaporation loss combined with mid-tip splash. A film of water coats the funnel and bucket walls every event and a portion evaporates before it tips — typically 0.1-0.3 mm per event. Across a wet month with many small showers, that adds up fast.
Check your event distribution. If most events are under 2 mm, evaporation loss dominates and a tipping bucket will systematically under-read versus a manual gauge that is read once a day. If events are mostly heavy, suspect mid-tip splash — confirm by comparing performance at low intensity (where they should agree) versus high intensity (where the tipping bucket under-reads).
Static calibration — pouring a known volume in slowly until it tips — only validates Vtip at near-zero intensity. To capture the high-rate error you need to deliver water at controlled flow rates spanning 10, 50, 100 and 200 mm/h equivalent and count tips against expected.
Use a peristaltic pump or a Mariotte bottle with a calibrated orifice. Plot measured-versus-expected at each rate and fit a polynomial. WMO Field Intercomparison protocols give the standard procedure. Without this, your high-intensity readings can be 10%+ low and you will not know it.
0.1 mm sounds better but the trade is real. A 0.1 mm bucket has half the volume so it tips twice as often, which doubles wear on the pivot and the reed switch over the gauge's life. It is also more sensitive to wind shake and to bucket-mass asymmetry — a 5 mg dust particle in a 0.1 mm bucket biases the tip point more than the same particle in a 0.2 mm bucket.
For flash flood and stormwater work where short-duration intensity matters, 0.1 mm is worth it. For agricultural and general climate logging, 0.2 mm gives plenty of resolution with longer mean time between failures and better behaviour in light wind.
That is reed switch contact bounce, not real rainfall. The seesaw cannot mechanically tip and re-tip in 50 ms — the natural period of the assembly is 100-200 ms. Reed contacts typically bounce for 1-3 ms but a worn or dirty contact can produce extended bounce strings.
Fix it in firmware with a debounce window of roughly 100 ms, or in hardware with an RC filter on the input. If the false counts persist beyond debouncing, the magnet may be mounted too close to the switch and is causing partial contact chatter as the seesaw oscillates against its stops after a tip — increase the magnet-to-switch gap by 1-2 mm.
Heated gauges melt snow but they also evaporate it. A funnel running at 5-10 °C above ambient generates a thermal plume that drives wind around the orifice and deflects falling snowflakes. Capture efficiency for dry snow drops to 50-70% in even light wind without an Alter or Nipher wind shield.
If you need snow-water-equivalent data, a weighing gauge with antifreeze charge is the right tool. Tipping buckets are a compromise on snow at best. Adding a single Alter shield around the gauge orifice typically recovers 15-25% of the lost catch.
Yes, for any application where the data drives a decision worth more than the second gauge. A single sensor cannot tell you when it has failed. Two gauges within a few metres should agree to within 5% on event totals — when they diverge by more than that, one of them has a problem (blockage, pivot wear, calibration drift) and you find out immediately instead of months later.
The WMO recommends paired gauges for any reference-quality climate site. For a vineyard or a small water utility, a backup gauge costs $200 and saves a season's worth of bad irrigation decisions when the primary clogs.
References & Further Reading
- Wikipedia contributors. Rain gauge. Wikipedia
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