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Air Velocity Flow Meter for HVAC Duct and Cleanroom Ventilation CFM Tracking
Quick Answer: An air velocity flow meter measures air speed in a duct and converts it to CFM when duct area is entered. For HVAC and cleanroom CFM tracking, Silver Instruments supplies insertion thermal mass meters with 4-20 mA HART output and local display. Send your duct size, velocity range, air temperature, and signal type for a quote.
In HVAC duct work, an air velocity flow meter gives a direct reading in m/s or FPM. Building engineers use this data to verify air balancing and fan performance. The same meter calculates CFM if you enter the round or rectangular duct dimensions. That helps with commissioning reports and cleanroom log sheets.
What an Air Velocity Flow Meter Does in an HVAC Duct
The meter measures air speed at the sensing point. A thermal mass sensor uses heat transfer from a heated element to the moving air. That method works well in clean air, HVAC supply ducts, and exhaust air with low moisture. The sensor has no moving parts. Because of that, it runs for years without wear.
For permanent installation, an insertion probe style is common. The probe inserts through a compression fitting or ball valve. A local display shows velocity and CFM. A 4-20 mA signal goes to the building management system.
Cleanroom Ventilation and CFM Tracking
Cleanrooms in pharmaceutical and electronics sites need stable air change rates. The supply air often passes through a duct before the fan filter unit. A fixed air velocity meter in that duct gives continuous CFM data. This is more reliable than manual spot checks with a hand held unit.
We have supplied meters for ISO Class 7 and ISO Class 8 rooms in Indonesia and the Philippines. One electronics assembly plant used 14 insertion probes on cleanroom supply ducts. They connected each probe to a central PLC with RS485 Modbus. The target duct velocity was 4.2 m/s.
Key Specifications Engineers Ask For
Specify the duct diameter, air temperature, velocity range, output signal, and probe length. For a typical HVAC duct of DN100 to DN250, a probe length of 150 mm to 300 mm is common. Silver Instruments can cut the probe to your insertion depth before shipment. Standard output is 4-20 mA with HART. RS485 Modbus is optional.
For cleanroom supply ducts, a velocity range of 0 to 10 m/s gives better resolution. For laboratory fume hood exhaust or chemical plant duct work, use 0 to 30 m/s. Standard air temperature rating is 0 to 80 °C. High temperature probes are available up to 120 °C.
Common Installation Mistakes We See
One common mistake is mounting the probe too close to a damper or elbow. The velocity profile is not stable there. Install the sensor at least 5 duct diameters downstream of a flow disturbance. For a DN150 duct, that means about 750 mm of straight run. If space is tight, use a field adjustable damping factor in the electronics.
Another issue is probe depth. In round ducts, the sensing element should sit near the c
Industries and Real Site Examples
A semiconductor assembly site in Malaysia needed CFM data from 22 cleanroom ducts. The data went to a central BMS with Modbus RTU. Silver Instruments supplied insertion thermal mass meters with a local display. Startup took half a day because the probe depth and 4-20 mA range were preset in the workshop.
A pharmaceutical packaging room in Thailand needed air flow verification after filter replacement. They installed fixed insertion probes on five critical supply lines. The cost was close to one week of manual testing by an outside calibration team. Now they log trend data every 30 seconds.
How to Order from Silver Instruments
Send us the duct diameter or duct dimensions, air velocity range, air temperature, required signal, and probe length. For hazardous area ducts, specify Zone 1 or Class I Div 2. We can supply ATEX or IECEx versions with flameproof enclosures. Standard delivery to Singapore, Manila, Dubai, and Sydney is 7 to 12 working days.
For project quotes, tell us the number of measurement points and the BMS input type. We also supply differential pressure transmitters for filter monitoring. Monitoring filter DP and air velocity together gives an early warning for fan or filter issues. Contact Silver Automation Instruments at Tel: +86-135-1213-1526 or WhatsApp: 86-135-12131526. WeChat: +86 13512131526.
Air Velocity Flow Meter FAQ
What is the difference between an air velocity meter and a CFM meter?
An air velocity meter reads speed in m/s or FPM. A CFM meter calculates volumetric flow using the duct area. Our insertion thermal mass meter can show both values once the duct dimensions are set.
Can one meter cover both low cleanroom velocity and high exhaust velocity?
One fixed range rarely gives the best accuracy at both ends. We suggest a 0 to 10 m/s unit for cleanroom supply air and a 0 to 30 m/s unit for exhaust. Tell us your minimum and maximum readings so we can set the right range.
Do you supply portable units or only fixed installation?
We supply fixed insertion meters for continuous monitoring. For spot checks, we can recommend a portable hot wire anemometer. Fixed meters are more useful for ISO cleanroom compliance logs and BMS integration.
How do I calculate CFM from duct velocity?
CFM equals velocity in feet per minute multiplied by duct area in square feet. For metric units, multiply m/s by duct area in square meters to get cubic meters per second. Our local display does the math after you set the duct dimensions.
What signal outputs are available?
Standard outputs are 4-20 mA with HART and RS485 Modbus. A local display and two relay outputs are optional. Tell the team your PLC or BMS input type before ordering.
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