The Psychrometer As A Weather Instruement
for Home WeatherForecasting
for Home WeatherForecasting
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In a psychrometer, there are two thermometers, one with a dry bulb and the other with a wet bulb. Evaporation from the wet bulb lowers the temperature, so that the wet-bulb thermometer usually shows a lower temperature than that of the dry-bulb thermometer, which measures dry-bulb temperature. When the air temperature is below freezing, however, the wet bulb is covered with a thin coating of ice and yet may be warmer than the dry bulb. Relative humidity is computed from the ambient temperature as shown by the dry-bulb thermometer and the difference in temperatures as shown by the wet-bulb and dry-bulb thermometers. Relative humidity can also be determined by locating the intersection of the wet- and dry-bulb temperatures on a psychrometric chart. One device that uses the wet/dry bulb method is the sling psychrometer, where the thermometers are attached to a handle or length of rope and spun around in the air for a few minutes.
A psychrometer is an instrument that measures relative humidity, much like a hygrometers. Both of these weather instruments perform similar jobs but each uses a separate method to measure humidity.
A psychrometer uses two separate thermometers. One of the thermometer's bulbs is dry while the other one is wet. The wet bulb is affected by the evaporation from the water, which has a tendency to lower the temperature. The dry bulb will reflect a higher temperature. If the ambient temperature is below freezing, a thin layer of ice coats the wet bulb and insulates the bulb. In this case the wet bulb may be a slightly higher temperature than the dry bulb.
The difference in temperatures between the wet and dry bulb readings is the "relative humidity." Another method of determining the relative humidity is by finding the intersection of the wet and dry bulb temperatures located on a special chart known as a "psychrometric" chart.
A type of psychrometer that is used frequently is called a "sling psychrometer." It either has a special handle from which it can be spun around or it is placed on the end of a piece of thin rope and spun around. This causes the bulbs of the thermometers to be subjected to the coolness of the air while at the same time being forced to their bottoms by the centrifugal force.
Relative humidity is important to determine the amount of suspended water particles in the ambient air.
There are cigar humidors that depend on relative humidity in order to keep the tobacco fresh. A sauna in a gym may also use a psychrometer to make certain that the humidity stays low in order to maintain a dry heat.
Modern weather instruments of all kinds often are found as digitally monitored and electronic in nature. Though the same wet/dry technique is used for psychrometers, the readings are sensed and read digitally. Sling psychrometers can still be found and purchased but for the home weather station enthusiast, the wireless digital models are usually more appealing
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Some popular psychrometer models include the Hygro-Thermometer with Programmable Humidity Alarm, Dew Point Reading, and Large LCD Screen
There are also sling psychrometers available online. A typical example would be the Bacharach 0012-7012 Sling Psychrometer