New Rain Sensor Improves Irrigation Control

A new optical sensing technology appears poised to change the way rainfall has been measured for centuries. Opto-Electronic Design, Inc. of Eden Prairie, MN has developed a optical infrared sensor that measures rainfall, the Rain Tracker RG-10 Rain Gage. The new rain sensor is about the size and shape of a tennis ball, and uses beams of infrared light to measure rainfall hitting its outside surface. There are no moving parts in the new sensor, so in addition to being a hundred times more sensitive than traditional tipping bucket-style rain sensors, the RG-10 is nearly indestructible.

With the gage, Irrigation control can be made more precise, and meteorology can be be made more mobile. The improved sensitivity of the RG-10 will make measurement of small amounts of rainfall possible. Weather reporters often report the rain as "a trace," rather than a giving an actual number, because the rain is simply not enough to tip the bucket in a traditional rain gauge.

Rainfall is typically measured with the tipping bucket-style of rain gauge that was invented in 1662. These work just as the name would imply: water collects in a large funnel and fills a bucket which tips when it reaches a certain weight.

Along with water, however, the funnel collects dust, leaves and other debris and mineral deposits, making it a maintenance item. Also, a tipping bucket sensitive enough to measure small amounts of rainfall is a delicate thing that may not be jostled. Other sorts of rain sensing technologies exist, each with other sorts of problems. In contrast, the RG-10 uses optical technology that was originally developed for automotive windshield wiper controls. Rain sensors for cars must be extremely sensitive and able to reliably withstand a harsh environment. This makes the RG-10 essentially maintenance free.

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