Tipping Bucket Rain Gauge

Build and calibration guide for the tipping bucket rain gauge, including sensor setup, funnel rim sizing, and screening.

How the Sensor Works

The tipping bucket rain gauge measures precipitation by collecting rainwater in a small bucket that tips when a certain volume is reached. With each tip, a magnet triggers an SS451A Hall effect sensor to record rainfall increments digitally, ensuring accurate and reliable data collection.

The tipping bucket rain gauge is calibrated to ensure each tip corresponds to a standardized rainfall depth (e.g., 0.2 mm per tip) using the volume of a cylinder to determine the required rim radius of the collector funnel.

Instruction Slides for Assembling the Rain Gauge

Tutorial Videos for Assembling the Rain Gauge

This video playlist demonstrates the entire assembly of the instrument. You can toggle between assembly videos using the "fast forward" and "rewind" buttons.

Calibrating the Rain Gauge

The rain gauge is calibrated through a multi-step process to ensure accuracy.

1. First, the tipping bucket mechanism is "bedded in" by cycling it approximately 1,000 times to reduce mechanical resistance.

2. Next, water is pumped into the funnel to generate around 500 tips, and the total volume of water that passes through is collected and weighed. By dividing the total water mass (grams) by the number of tips, the system determines the grams of water per tip.

3. Using the density of pure water (1 gram = 1,000 mm³), this mass is converted to volume (mm³).

4. The target rainfall depth per tip—0.2 mm is then applied to the volume of a cylinder formula (V=πr²h).

5. Rearranging the equation to solve for radius , the funnel’s rim size is calculated to ensure each tip corresponds precisely to the desired rainfall depth.

$$r = \sqrt{\frac{V}{\pi h}}$$

This process bridges empirical testing (weighing water) with geometric principles (cylinder math), ensuring the gauge meets standardized meteorological requirements.

Please use the Rain Gauge Calibration Spreadsheet as an aid in the calibration process

Using a Raspberry Pi to Calibrate the Rain Gauge

Testing the Sensors

Instruction Slides for Calibrating the Rain Gauge

Note: Due to the constant adjustment of the Pumped Drip Controller, we have moved to a new method of controlling the flow rate for calibration.

Tutorial Videos for Calibrating the Rain Gauge

This video playlist demonstrates the entire assembly of the instrument. You can toggle between assembly videos using the "fast forward" and "rewind" buttons.

Adding the Screens

The rain gauge screen serves as a protective barrier, preventing debris from entering the funnel and interfering with the tipping bucket mechanism. By filtering out leaves, twigs, and other particles, it ensures accurate and reliable rainfall measurements. This screen is crucial for maintaining the gauge's precision and longevity, especially in outdoor environments where debris accumulation is common.

Instruction Slides for Adding the Screens