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How to Calibrate a Tipping Bucket Rain Gauge

Invented in 1662 by Sir Christopher Wren, the tipping bucket rain gauge is the oldest remotely operated, automated design that does not require direct observation to compile a record of rainfall. Modern tipping buckets employ a funnel to collect rainfall and channel it into one of two buckets on opposite ends of a balanced seesaw. When the amount of rain in bucket 1 reaches a pre-set volume sufficient to unbalance the seesaw, the bucket tips, actuating a micro-switch, which records the tip on a graph, a paper punch tape or transmits it wirelessly. As bucket 1 drains its contents, bucket 2 raises into the collection position, fills with rain and tips, actuating the micro-switch again. By this method the bucket tips/switch actuations are tabulated and converted into an accurate measure of the amount of rain falling over a given period of time. Proper calibration of the tipping bucket rain gauge is important to accurately determine the amount of rain.

Things You'll Need

Laboratory burette
Empty gallon containers
Calibrated measuring containers

Instructions

- 1
  Verify that the collecting funnel and buckets are clean and free of debris such as leaves and sediment.
- 2
  Make sure the tipping bucket mechanism is situated on a level surface.
- 3
  Pour water in an amount approximately equal to five buckets into the collecting funnel to check the general mechanical operation of the mechanism. Verify that the buckets tip the proper number of times for the amount of water added.
- 4
  Adjust a calibrated laboratory burette to slowly drip 300mm of water into the collecting funnel at a rate of 10mm per hour. Set up two containers to collect the contents of each bucket tip separately.
- 5
  Check the number of bucket tips recorded after all the water has passed through the gauge. Divide the amount of water by the number of bucket tips to determine the average volume of water per bucket tip. Compare this amount to the manufacturer's specification for the gauge.
- 6
  Measure the amount of tipped water in the two separate containers. The values should be nearly identical. Divide the amount of water for each bucket by the number of tips recorded for that bucket. If the volume per tip of either bucket is more than 2 percent below or above the specification for the gauge, follow manufacturer's procedure to adjust the bucket stop for that bucket.
- 7
  Repeat the procedure to verify the results after the adjustment.

Nature