Tuesday, April 24, 2007
Why is it so windy in Reno?

Here is an interesting illustration from the Reno Gazette-Journal that explains why very high winds frequently blow in the valleys just to the east of the Sierra Nevada. The predominant wind blows from west to east over the Sierra Nevada and high winds aloft, associated with storms, spill down the lee side of the mountain range following the terrain. These winds of 50 mph or greater spill out onto the valley floors. Winds in the Washoe Valley south of Reno are frequently of sufficient strength to over turn large semi trucks and trailers. The drawing shows how this effect works. This kind of down slope gusting is not unique to the Sierra Nevada. Those of you who live along the Front Range of the Rocky Mountains are familiar with the same effect.


Friday, April 13, 2007
Wind Direction Potentiometer Configuration
360° Format: For years a 360° potentiometer has been the standard for measuring wind direction. Because the resistance element of the potentiometer is roughly 358°, there is a "dead area" or "slot" of approximately 2°. This opening in the pot is customarily oriented to the north. The 360° format is extremely well suited to applications where a display indicator is used, either alone or with analog recording instrumentation. Its disadvantage is that when the wind is from the north readings will vary between maximum to minimum output as the wiper in the pot goes back and forth across the slot, thereby causing a pen trace across the full width of an E-A recorder or presenting numerous other complications for computer data logging.

540° Format: In recent years, a new configuration has been used quite successfully. Two potentiometers are joined together with wipers in the pots 180° from each other, thus providing a 540° uninterrupted display. This convention of dual potentiometers has greatly minimized the problems encountered in 360° displays. The signal conditioning provides automatic switching between the two pots.

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Friday, April 6, 2007
Algae Control in Evaporation Pans
evaporation pan

An evaporation pan must be cleaned frequently to keep it free from sediment, algae, and oil films. Any of these contaminants will materially affect the rate of evaporation.

The growth of algae can be discouraged by adding a small amount of copper sulfate to the water. (Approx 5-10 mg of copper sulfate per liter of water.) A standard Class A pan filled to 8 inches would require about 1/2 teaspoon of copper sulfate granules.

If algae is already present, it must be removed first by thoroughly cleaning the pan. Dry granules added directly into the pan will sink to the bottom and may not dissolve completely. If you have this problem, the granules can be dissolved in water before being added to the pan or placed in a burlap bag and dragged around the pan until dissolved.

It's not necessary to add additional copper sulfate each time you add water to the pan. The copper sulfate doesn't evaporate with the water but remains in the pan.

Copper sulfate is corrosive and can be toxic to animals and fish, so it must be handled with care and disposed of properly. Copper sulfate can be purchased at feed and agricultural supply stores, garden centers, and pet supply stores.

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