Rain Gauges

KI5OMM weather station

The rain gauge that I use for the KI5OMM weather station is a tipping bucket design. This allows for automatic and unattended operation. This type of rain gauge is fairly accurate for most rainfall events. They do have a few flaws that can lead to errors in reporting. For this reason, I also use a manual 4″ rain gauge for backup. Here is a description of my setup and design for my station.

KI5OMM Weather Station

My automatic rain gauge is a standard Davis Instruments design. This consists of an internal tipping bucket that trips a reed switch with each tip. This is calibrated to report .01 inch of rain for each tip of the bucket.  This is a simple design mechanically and very reliable with only one moving part. The design does have some shortcomings though that become apparent during very heavy rainfall events. Water droplets can splash out of the internal bucket leading to errors in measurement. In spite of precise calibration of the bucket halves at the factory when manufactured, over time the bucket can become out of balance.

KI5OMM Weather Station

The rainfall in my area is usually fairly acidic which is evident by the erosion of the chrome off of the plastic as seen here. This can lead to small errors in calibration which can add up to measurable amounts over long periods of time. All things considered, my Davis rain gauge is still accurate and useful for it’s automatic and unattended operation.

For my official rainfall report to CoCoRahs, I use an accurate 4″ standard tube type rain gauge.

KI5OMM Weather Station

This design uses a funnel at the top to collect rain droplets that flow into an internal measuring tube. Once this tube is full, it overflows into the outer 4″ tube. The inner tube holds exactly 1″ of rain before it overflows. The measuring gauge on the side is accurate to within .001 inch. If more than one inch of rain has occurred the contents of the outer tube is carefully poured into the inner tube after dumping out the initial one inch. The sum of the measurements is then read as the total rainfall. This is a basic and very accurate design that has been used for many years. The biggest disadvantage is human error. Primarily due to my laziness, I don’t really want to go outside on a rainy and cold morning to read the rain gauge. It is much more convenient to read the Davis electronic gauge from inside the room! I have the gauges mounted side by side in the same location and it has been my experience that both gauges are accurate and read nearly identical amounts of rain. During an extreme storm event however, I would rely on the manual 4″ gauge for the official station record.

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