Instrumentation

Anemometer

Anemometer

Introduction:

The term is derived from the Greek word anemos, meaning wind. An anemometer is a device for measuring wind speed, and is a common weather station instrument.
The first known description of an anemometer was given by Leon Battista Alberti around 1450.

Anemometers can be divided into two classes: those that measure the wind’s speed, and those that measure the wind’s pressure; but as there is a close connection between the pressure and the speed, an anemometer designed for one will give information about both.

Types:

  Three cup anemometers

1)Windmill anemometers

2)Hot Wire / Film Anemometer

3)Laser Doppler anemometers

4)Sonic anemometers

Operating Principle :

Hot wire anemometers use a very fine wire (mm) electrically heated up to some temperature above the ambient. Air flowing past the wire has a cooling effect on the wire. As the electrical resistance of most metals is dependent upon the temperature of the metal (tungsten), a relationship can be obtained between the resistance of the wire and the flow speed.

Several ways of implementing this exist, and hot-wire devices can be further classified as

  • CCA (Constant-Current Anemometer)
  • CVA (Constant-Voltage Anemometer)
  • CTA (Constant-Temperature Anemometer)

The voltage output from these anemometers is thus the result of some sort of circuit within the device trying to maintain the specific variable (current, voltage or temperature) constant.

 

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