Company Profile

Air Velocity Meters and Anemometers: Precision Airflow Trackers for HVAC Ventilation

Quick Answer: Silver Instruments supplies air velocity meters and anemometers for HVAC airflow measurement from 0 to 40 m/s. Output options include 4-20 mA HART, RS485 Modbus, and pulse. These devices fit round ducts from DN50 to DN300 and rectangular ducts with probe or flange mounting. Send duct size, airflow range, signal output, and probe length for a firm quote.

Airflow measurement in HVAC is not the same as water flow measurement. A small offset in an air velocity sensor can hide a 20 percent ventilation shortfall. We have seen this on customer sites many times. One building products plant in Vietnam had three rooftop units running at full speed because a faulty vane sensor never reached its minimum start velocity. The result was high energy cost and noisy ductwork.

Air Velocity Meter Types We Supply for HVAC

We offer three main sensor types for HVAC and building management. Choose based on duct size, air speed, dust level, and whether you need temperature compensation.

Thermal anemometers work best for low air velocities. A typical range is 0 to 1 m/s, 0 to 2 m/s, 0 to 10 m/s, or 0 to 20 m/s. They use a heated element and measure cooling effect. These units are common in cleanrooms, labs, and VAV boxes. Accuracy can be ±0.1 m/s or ±0.2 m/s depending on the model. Output is normally 4-20 mA with HART or RS485 Modbus.

Vane anemometers cover higher air velocities. A 100 mm vane probe can read from 0.3 m/s to 40 m/s. A 16 mm mini vane can start from 0.4 m/s. These sensors suit supply air ducts, return air risers, and exhaust stacks. They are less sensitive to dust than thermal probes but still need periodic cleaning.

Pitot tube transmitters use differential pressure. They are a good fit for hot air, dirty air, and large industrial ducts above DN300. The velocity range depends on the differential pressure cell. Common ranges are 0 to 10 m/s, 0 to 20 m/s, and 0 to 40 m/s. A pitot averaging probe can work in a rectangular duct up to 2 m wide.

Key Specs That Matter on an RFQ

Most engineers skip this part. Do not skip it. A missing probe length or signal type causes delays longer than the price quote itself.

Specify the duct shape and size. Round ducts use DN or internal diameter in mm. Rectangular ducts use width by height in mm. Probe length should cover at least 70 percent of the duct cross section. For a DN200 round duct, a 150 mm probe is common. For a 600 mm by 400 mm rectangular duct, a 400 mm probe is safer.

Specify air velocity range. HVAC supply air often runs at 2 to 8 m/s. Return air can be 1 to 4 m/s. Fume hood face velocity is 0.4 to 0.6 m/s. Cleanroom airflow can be 0.2 to 0.5 m/s. If the range is too wide, you lose resolution. If it is too narrow, you may saturate the sensor.

Specify signal output. Our standard outputs are 4-20 mA two wire, 4-20 mA HART, RS485 Modbus RTU, and pulse. We can add a local LED display or a handheld meter. Temperature compensation is available with a PT100 or a built in digital sensor. The typical compensated temperature range is -20 to 80 °C for HVAC. The media temperature can reach 120 °C for hot flue gas with a separate pitot tube design.

Specify installation style. Options include insertion probe with compression fitting, flange mount, wall mount for handheld anemometers, and hot tap retractable probe. Enclosure rating is usually IP65. For outdoor rooftop units we recommend a weather shield and cable gland.

Hot Wire vs Vane vs Pitot: What to Choose in Practice

Here is the thing. No single meter fits every HVAC job. Thermal probes are accurate at low speed but fail fast in dusty or oily air. Vane probes handle higher flow but have a minimum start velocity. Pitot tubes survive dirt and heat but need a stable differential pressure transmitter and regular purge air