Simple weather instruments let you track weather conditions.
Setting up a home weather station is an interesting and educational activity for both young and old. To get a good idea of what the weather conditions are like where you live, you'll need devices to measure barometric pressure, humidity, temperature and wind speed. Instruments for measuring weather don't have to be expensive or complicated; you can purchase them cheaply or even build your own.
Measuring Temperature
Thermometers measure the temperature of the surrounding air.
How hot or cold it is outside affects nearly everything you do. The clothing you where and what activities you engage in all affected by the temperature. A thermometer is a simple device used to measure how hot or cold the air around it is. The simplest thermometers consist of a sealed glass tube with a large bulb on one end. The tube is partially filled with alcohol or colored water that changes its level as the temperature surrounding it rises and falls. There are numbers printed on the thermometer, and the level of the fluid in the glass tube will match up with the numbers so that you can see what the temperature is. Other thermometers are digital, and use a heat-sensitive thermocouple to measure the temperature of the environment around them. The temperature is displayed on a small screen in degrees Fahrenheit or Celsius.
Measuring Humidity
A hygrometer lets you determine the humidity of the air.
Humidity, the amount of water vapor in the air, is another important factor that influences the weather. A hygrometer is a simple device used to measure the amount of humidity in the air. Because humidity is difficult to measure directly, hygrometers measure humidity by measuring the effect that humidity in the air has on a part of the device. One of the earliest types of hygrometer used human hair or horsehair to indicate the amount of water vapor in the air. If you have curly hair, you may have noticed that your hair is harder to handle on humid days. This is because hair relaxes and gets longer as it absorbs moisture. Humidity in the air can also affect temperature and barometric pressure. Using a hygrometer to determine the humidity of the air can help you predict precipitation.
Measuring Wind
A weather vane indicates wind direction.
The wind is produced by changing masses of hot and cold air. There are several simple devices useful for measuring both wind speed and direction. A weather vane points in the direction that the wind is coming from because the rear portion of the weather vane has a larger surface area than the arrow in front. When the wind blows, it pushes the larger rear panel around in the direction the wind is blowing, and the arrow points in the direction the wind is coming from. Placing indicator markers underneath the weather vane aligned to North, South, East and West allow you to see exactly which direction the wind is coming from. An anemometer is a simple instrument for calculating wind speed. It consists of a set of shallow cups mounted on arms connected to a shaft. When the wind blows, the cups spin around the shaft; by counting the number of rotations over a given period of time, you can calculate wind velocity.
Measuring Atmospheric Pressure
A barometer measures atmospheric pressure.
Atmospheric pressure is an important factor for predicting changes in the weather. The atmosphere exerts pressure on the surface of the earth that can vary as temperature and humidity change. Falling atmospheric pressure indicates a possibility of inclement weather, while rising air pressure tends to predict fair weather. A barometer is a simple instrument used to measure the rising and falling of atmospheric pressure as weather conditions change. Some barometers operate by measuring changes in the level of mercury in a sealed glass tube. Others use a small capsule that has had the air inside it removed. These aneroid barometers have indicator hands that move as the pressure of the outside air compresses the capsule or allows it to expand.
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