Which instrument is commonly used to measure velocity pressure in a duct during air balancing?

Which instrument is commonly used to measure velocity pressure in a duct during air balancing?

• A. Anemometer vane with no pressure measurement
• B. Pitot tube paired with a manometer or digital differential pressure sensor
• C. A moisture meter
• D. A thermocouple

Answer: (B)

Velocity pressure is the dynamic pressure from moving air that you use to calculate airflow in a duct. The instrument that directly provides this pressure in the field is a Pitot tube used with a static port and a device to read the pressure difference. The Pitot tube captures stagnation (total) pressure, while static ports sense the ambient static pressure. The difference between them is the velocity pressure, which you then read on a manometer or a digital differential pressure sensor. This setup gives you the exact quantity needed to compute air volume through the duct, using the duct size and calibration. Other tools in the list don’t provide this essential pressure difference: a vane anemometer alone gives velocity at a point but not the velocity pressure needed to derive flow; a moisture meter and a thermocouple measure moisture and temperature, respectively, not airflow.

Velocity pressure is the dynamic pressure from moving air that you use to calculate airflow in a duct. The instrument that directly provides this pressure in the field is a Pitot tube used with a static port and a device to read the pressure difference. The Pitot tube captures stagnation (total) pressure, while static ports sense the ambient static pressure. The difference between them is the velocity pressure, which you then read on a manometer or a digital differential pressure sensor. This setup gives you the exact quantity needed to compute air volume through the duct, using the duct size and calibration.

Other tools in the list don’t provide this essential pressure difference: a vane anemometer alone gives velocity at a point but not the velocity pressure needed to derive flow; a moisture meter and a thermocouple measure moisture and temperature, respectively, not airflow.