How Does a Tipping Bucket Rain Gauge Work?

A tipping bucket rain gauge is a meteorological device that measures the amount of precipitation, or rain, that has fallen. It is one of the most common tools used to measure rainfall. Tipping bucket rain gauges are a really interesting and fun way for you and your children to learn about the weather and predict what the weather will be in your area. A tipping bucket rain gauge has several components that allow it to accurately measure of rainfall. As rain falls it lands in the funnel of the tipping bucket rain gauge. The rain travels down the funnel and drips into one of two very carefully calibrated ‘buckets’ balanced on a pivot (like a see-saw).

The top bucket is held in place by a magnet until it has filled to the calibrated amount (usually approximately 0.001 inches of rain). When the bucket has filled to this amount, the magnet will release its hold, causing the bucket to tip. The water then empties down a drainage hole and raises the other to sit underneath the funnel. When the bucket tips, it triggers a reed switch (or sensor), sending a message to the display or weather station.

The display counts the number of times the switch is triggered. Because it knows how much rain is needed to fill the bucket, the display can calculate the rainfall. Rainfall is measured in inches; 1″ of rain would fill a container with straight edges to a level of 1″.

To get the most accurate results from a tipping bucket rain gauge, you need to properly install the rain gauge.

  1. The rain gauge must be positioned on a flat surface – if the surface isn’t flat, the see-saw may tip before the bucket has filled to the calibrated level, or not tip at all. If the bucket doesn’t tip at the calibrated level, the rainfall calculated will not be correct. Use a spirit level to determine whether a surface is flat, and then fix the gauge to the flat surface to ensure you are getting an accurate reading.
  2. The rain gauge must be positioned on a surface that does not vibrate – surfaces such as a porch or fence can move and vibrate. The tipping bucket is very sensitive and any vibrations could cause the gauge to tip even if it is not raining.
  3. The instrument must not be positioned near trees – being positioned near trees could allow leaves or pollen to fall inside the funnel and block it, causing an inaccurate reading.
  4. It must not be positioned in a sheltered area – Being positioned in a sheltered location (such us beside your house or a fence) could significantly increase or decrease the amount of rain depending on the wind direction, and cause an inaccurate reading. The gauge should be positioned at least twice as far away from the object as the object’s height (e.g. if the fence is 6 feet high, the gauge should be positioned at least 12 feet away).
  5. Your weather equipment must not be located near any magnetic, steel, or iron objects – magnetic, steel, or iron objects can affect the amount of time the magnet will hold the bucket or whether it will hold it all, causing an inaccurate reading.