3. Rain Gauge Calibration

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

Tutorial Videos

This video playlist demonstrates the entire assembly of the instrument. You can toggle between videos using the list icon at the top right or by using the "fast forward" button at the bottom left.

Instruction Slides

Note: for rain gauge calibration using the drip bottle method, please reference the 3D-PAWS Manual 2022 (Qwiic cables) under Previous Manual Versions

Rain Gauge Calibration - Slides