The Application
Over 90 % of the available water supply in the western United States is generated by melting snow in the Rocky, Cascade, and Sierra Nevada mountains. The ever changing weather patterns and the public demand for water requires accurate forecasting for the amount of "stored water" in the mountain snow pack.
These forecasts for the amount of stored water are essential for the effective allocation of these resources. There are nearly 1000 weather measurement stations throughout these mountains to monitor a variety of weather parameters including precipitation.
The schematic in figure 1 illustrates a typical remote weather station, some of which are only accessible by helicopter, snowmobile or on foot and mule train. The remote locations of these weather stations, and the harsh environment demanded extremely reliable pressure transducers to sense the snow depth and precipitation.
Summary
Sensotec engineered and built special pressure transducers to monitor the depth of the snow pack at remote mountain site weather stations. These mountain site locations have very harsh environmental requirements with wide seasonal temperature and humidity swings as well many unfriendly critters that often threatened the function of the instrumentation, and site equipment in general.
As a result of many successful weather site installations, the customer could anticipate water supply issues and take the necessary steps to meet the public's needs.
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The Solution
Sensotec was able to supply these reliable transducers which required two sensors at each remote weather station. One transducer was connected to a precipitation gauge which measures the liquid pressure (level) in an open cylinder container of an antifreeze solution plus dissolved snow. The other transducer was connected to a snow pillow about the size of a water bed that was filled with an antifreeze solution. The snow level in these mountains can be above 50 feet, and the snow weight creates a proportional liquid pressure increase inside the snow pillow which measured by the Sensotec transducer.
By combining these pressure measurements with temperature, and humidity, etc., an accurate calculation can be made of the actual depth of the snow pack. The entire weather station is powered by batteries with solar chargers, including a radio transmitter that transmits all the data to a distant water and climate control center for analysis.
The combined requirements of the pressure transducer to operate was over a wide temperature, pressure range, and input power. These specifications and the mechanical requirements did not match any of our standard products. We were able to design and build a pressure transducer which met and exceeded many of the customer's requirements and Sensotec won the contract.
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