Heated Wire Anemometer: Direct Reading Instrument

Heated Wire Anemometer: Direct Reading Instrument

• A. Measuring Velocity
• B. Total Pressure (TP)
• C. Field Blanks (FB)
• D. Media Blanks (MB)

Answer: (A)

A heated wire anemometer directly measures how fast air is moving. It uses a very fine wire that is heated by electricity. When air flows past the wire, it cools the wire—the hotter the air, the more cooling occurs. The instrument adjusts the current to keep the wire at a constant temperature (or constant resistance). The current needed to maintain that temperature is proportional to the cooling, which depends on the air velocity. So the device provides a direct reading of air velocity in the space or duct. This isn’t a measure of total pressure, which would require a pressure-sensing setup like a Pitot tube and a manometer. It also isn’t about field blanks or media blanks, which are quality-control samples used to detect contamination rather than to measure airflow.

A heated wire anemometer directly measures how fast air is moving. It uses a very fine wire that is heated by electricity. When air flows past the wire, it cools the wire—the hotter the air, the more cooling occurs. The instrument adjusts the current to keep the wire at a constant temperature (or constant resistance). The current needed to maintain that temperature is proportional to the cooling, which depends on the air velocity. So the device provides a direct reading of air velocity in the space or duct.

This isn’t a measure of total pressure, which would require a pressure-sensing setup like a Pitot tube and a manometer. It also isn’t about field blanks or media blanks, which are quality-control samples used to detect contamination rather than to measure airflow.