RSES Journal Winter 2025, RETA-RSES

Mechanical Rotating Vane Anemometer

Digital Rotating Vane Anemometer

Typical Specification

Thermal Anemometer

Velocity Grid/Matrix

Airfoil-Airflow Probe

Flow Hood- Capture Hood

Pitot Tube

25–2500 CFM (1500 CFM exhaust)

Measurement Range

200–10,000 ft/ min

0–6000 ft/min

50–6000 ft/min 25–2500 ft/min 25–5000 ft/min 50–8000 ft/min

Temp. range

40°F–113°F

40°F–113°F

40°F–140°F

40°F–140°F

40°F–140°F

40°F–140°F

±5% of reading or ±5 ft/min, which ever is greater

±1% of reading or ±4 ft/min, which ever is greater

Micro-manom eter will report negative value Micro-manom eter will report negative value Face velocity (grill, lab/kitchen hood, filter, coil); traverse; point air velocity; low velocities

±3% of reading ±7 ft/min

±3% of reading ±7 ft/min

±3% of reading ±7 CFM

Accuracy

Micro-manom eter will report a “NegPitot” or “Error”

Micro-manom eter will report negative value

Micro-manom eter will report negative value

Reports positive in both directions

Vane will rotate backwards

Vane will rotate backwards

Airflow direction

Face velocity (grill, lab/kitchen hood, filter, coil); traverse; point air velocity

Face velocity (grill, lab/kitchen hood, filter, coil)

Face velocity (grill, lab/kitchen hood, filter, coil)

Face velocity (grill, lab/kitchen hood, filter, coil)

Duct Traverse; plenum traverse

Diffuser, outlet grill, etc.

Applications

Typical specifications for various manufacturers are noted. Consult individual manufacturer for specific technical data. Location of an instrument within the airstream, velocity profile and application of instrumentation will affect velocity measurement.

spheric pressure at mean sea level accord ing to the Inter national Standard Atmosphere (ISA). This value serves as a universal reference for pressure-related calcu lations and instru ment readings. Test and Balance (TAB) density correc tions shall be made when temperatures

Electronic manometers from Shortridge and Evergreen Telemetry.

are greater than or less than 30°F of stan dard air, or if the altitude is greater than 2000 ft above sea level. Applying density correction factors allows technicians to convert indicated cubic feet per minute (CFM) readings to the actual CFM under standard condi tions, ensuring that the system is operat ing according to its design specifications. The best practice is to make a 2% correc tion for each 1000 ft above sea level, and a 1% correction for each 10°F above or below 70°F. Proper Instrument Application The technician’s goal when using airflow testing instruments is to record accu rate and repeatable measurements. This requires proper use of the instruments, an understanding of instrument operation and limitations; reliable system design and operation; and a good velocity profile.

Acceptable and unacceptable velocity profiles. Reprinted from “AMCA Publication 201-90, Fans and Systems.” Reprinted by permission from AMCA.

WINTER 2025 RSES Journal 15

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