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Ultrasonic measurement for air

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Ultrasonic flowmeters for air - FWD

Non-intrusive design free from pressure loss

Ideal for control compressor, air leakage detection, visualization of the compressed air use and all air concentration measurement and energy saving.


  • Abundant applicable pipe diameters: From Ø25 to Ø200 mm
  • No energy loss: Non-intrusive ultrasonic sensor causes no pressure loss
  • Tolerant to Oil Mist: With no moving parts, FWD is robust, and requires no filters.
  • Battery powered version: The version equipped with a lithium-ion battery (10-year life) greatly lightens the installation work.
  • Flow rate conversion: Measured flow rate can be converted into a flow rate under normal conditions of a temperature of 0 degree C (273.15 K) and an absolute pressure of 1 atm or user-defined conditions.)
  • Bi-directional flow measurement: FWD can measure the air transfered between facilities, and the air flow in loop piping system.

Measurement principle

Two ultrasonic sensors are installed on each side of the flowmeter input and output. measurement principleWhen liquid flows (in the direction of the arrow shown on the diagram), difference of transit time by flow velocity occurs between sound waves generated from flow entrance and exit. This time lag is used for detecting the flow velocity of the fluid and calculating the volumetric flow according to cross-section area of the flow meter and flow velocity.
Furthermore, this flowmeter is capable of converting into NORMAL flow rate by means of build-in pressure sensor in the flowmeter.



Pipe diameter (mm) 25, 32, 40, 50, 65, 80, 100, 150, 200   
Power supply24 V DC ±10% or Built-in battery type (battery life : approx.10years at 20˚C)   
Power consumption24 V DC, 1.5 W or less   
Applicable fluidsAir (mainly air factory) or Nitrogen (25-80 mm diameter)   
Teperature and humidity of fluid10°C to 60°C, RH 90% or less   
Working pressure0 to 1 MPa (gauge pressure)   
Range (actual flow rate) and accuracy DiameterRange (m3/h) Accuracy
±2.0% of rate±0.6–3.5 m3/h
25±0.6–35±3.5–35 m3/h±0.6–3.5 m3/h
32±1.1–65±6.5–65 m3/h±1.1–6.5 m3/h
40±1.3–80±8–80 m3/h±1.3–8 m3/h
50±2.5–150±15–150 m3/h±2.5-15m3/h
65±4–240±24–240 m3/h±4–24 m3/h
80±5–300±30–300 m3/h±5–30 m3/h
100±10–500±50–500 m3/h±10–50 m3/h
150±24–1200±120–1200 m3/h±24–120 m3/h
200±40–2000±200–2000 m3/h±40–200 m3/h
Flow rate conversion accuracy FWD 025–080 : ±2.5% or rate (at 500 kPa, 25°C, dry air)
FWD 100–200 : ±2.0% or rate (at ≥ 300 kPa)
DisplayMain displayForward or forward/reverse mode :
  • Ø25–Ø80 mm : Instantaneous flow rate (m3/h) 5-digit (4-digit for over 2000), Pressure (kPa) 5-digit, temperature (°C) 3-digit
  • Ø100–Ø200 mm : Instantaneous flow rate (m3/h) 5-digit (4-digit for over 2000), Pressure (kPa) 5-digit, Temperature (°C) 3-digit
Sub display
  • Ø25–Ø80 mm: Instantaneous flow rate (Nm3/h) 5-digit (4-digit for over 2000), Pressure (kPa) 5-digit, temperature (°C) 3-digit
  • Ø100–Ø200 mm: Instantaneous flow rate (Nm3/h) 5-digit (4-digit for over 2000), Pressure (kPa) 4-digit, Temperature (°C) 3-digit
Output signal
(not available for battery-driven version)
Current ouput4–20 mA DC (±0.5% FS), maximum resistance load 400Ω, maximum output current 22 mA
Instantaneous flow rate, pressure, or temperature
Contact output
  • 2 open drain outputs, maximum load 24 V DC, 50 mA, maximum frequency : 10 Hz, Duty 35–65%
  • Output 1: Unit pulse (forward), Output 2 : Unit pulse (reverse), Upper/lower alarm, device error
Connection methodØ25, Ø32 mmØ25 mm : Rc1, Ø32 mm : Rc1-1/4
Ø40–Ø80 mmWafer (between JIS10K flanges)
Ø100–Ø200 mmJIS10K flange
Materials of gas-contacting parts Aluminum alloy, PPS, fluorosilicone rubber, etc.
Installation location Indoor or outdoor (IP64 equivalent)
Storage temperature -20°C to 70°C, non condensing


Ultrasonic measurement for air documentation