1. Working Principle: A very thin wire (usually platinum or tungsten) is heated to a temperature above the ambient fluid temperature by passing an electric current through it.
2. Convective Cooling: As gas flows over the heated wire, it removes heat from the wire through convection. The amount of heat removed is directly related to the
velocity of the gas.
3. Modes of Measurement:
• Constant Current Mode: The current is held steady, and the change in wire resistance (due to cooling) is measured.
• Constant Temperature Mode: The wire is kept at a constant temperature by adjusting the current. The amount of current required to maintain that temperature is a measure of the gas velocity.
Due to its high sensitivity and ability to measure rapid fluctuations, the hot-wire anemometer is the standard tool for measuring gas velocities in turbulence and aerodynamics studies.