Hot wire anemometer

This type of flow meter consists of a thin platinum wire, electrically heated to constant temperature, and centrally located in a tube. As gas passes through the meter the wire cools off, requiring extra electrical energy to maintain its temperature. The extra electrical energy is a measure of gas flow.

• A chip is required to linearize the output of hot wire anemometers.
• As anemometers are insensitive to the direction of flow, two heated wires need to be placed in series; the flow direction can then be determined from the wire that cools first.
• A disadvantage of this type of meter is its sensitivity to gas composition and gas temperature; in addition these measuring systems are very vulnerable to damage and need to be handled with special care.