Flow sensors and flow meters

Flow sensors and flow meters are essential components for measuring and monitoring the flow of liquids and gases. They are used in industry, laboratories, water treatment, ventilation, heat exchangers, compressors and medical applications.

At Swelex you'll find reliable solutions that ensure efficient process control and proper distribution of liquids and gases.

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What is the difference between flow sensors and flow meters?

  • Flow sensors: Converts flow into an electrical signal (4-20 mA, 0-10 V or digital), for integration into control and monitoring systems.
  • Flow meters: Displays the flow directly, often with a visual indicator (paddle wheel, float, rotor), and is used where the measurement value needs to be read on site.

Both types can be combined for precise control and alarm functions in systems.


Henke Sass Wolf DW-D Flow sensor

Digital paddlewheel flow sensor with analogue output and totalizer, ideal for liquids and gases.

  • Patented sensor principle with pendulum system
  • Digital display, analogue output signal (4-20 mA, 0-10 V)
  • Totaliser and two adjustable switch points
  • Large measuring range and high precision


Gems FT-110 Flow sensor

Hall Effect turbine flow sensor for low flows, ideal for OEM.

  • Flow rate 0.5-30 l/min
  • Accuracy ±3 % of reading
  • Mounting in any direction
  • Electrical output signal for connection to control system


Gems RFO-PW Flow sensor

FDA approved rotor flow sensor for drinking water applications.

  • Pulsed VDC output (4-25 VDC)
  • Visible blue rotor for easy control
  • Stainless steel sensor housing
  • Compact and panel-mountable


Gems RFS series

Electronic rotor flow sensor with visual indicator and adjustable switch function.

  • Easy adjustment of switching points
  • LED indication at set flow rate
  • Suitable for medical equipment, laser systems & robotic applications
  • 115 VAC operation


Gems FT-330 Flow sensor

Hall Effect turbine flow sensor for low flow, high precision applications.

  • Flow rate 0,8-7,6 l/min
  • Accuracy ±2 % of reading
  • NSF certified
  • Overmoulded electronics with integrated cable reinforcement


Dwyer IEF Series Flow Sensors

Electromagnetic flow sensor with field-configurable installation and multiple outputs.

  • High accuracy and multiple continuous signal outputs
  • Communication protocol: BACnet MS/TP or Modbus RTU via RS-485
  • Analogue, frequency and alarm outputs
  • Fits pipe sizes 4-36 inches (101-914 mm)


Gems RFI-PW Flow meter

FDA compliant rotor flow meter for drinking water with visual rotor.

  • Rotorflow technology with blue rotor
  • Bayonet-mounted lens for quick cleaning
  • Easy to install and cost-effective
  • Material: nylon and epoxy


Dwyer RM Series Flow Meters

Polycarbonate float flowmeter with panel or surface mounting, flexible for gases and liquids.

  • Scales: 2″, 5″ or 10″
  • Interchangeable bodies without shutdown
  • For medical equipment & chemical dosing systems
  • Precision and direct reading


Dwyer VF Visi-Float Series Flowmeters

Precise flow meter with visual indicator for low flow applications.

  • Acrylic body with high durability
  • 2″ and 4″ scales
  • For laboratories, medical equipment & gas analysis
  • Can be equipped with precision metering valves

Applications

  • Industrial processes: Monitoring of liquid and gas flows in pipework, pumps and heat exchangers.
  • Water and wastewater treatment systems: Ensures proper distribution and treatment of water.
  • Laboratories & medical applications: Accurate measurement of low flows and gases.
  • Ventilation & HVAC: Optimises air flows, filter monitoring and pressure control.
  • Compressors and turbines: Protects equipment against over- or underflow.

Types of flow sensors

  • The pendulum principle / Paddle Wheel- Mechanical or non-contact flow detection.
    - Simple construction with a long service life.
    - Can provide electrical output for control systems.
    - Flexible for different flow rates.
  • Ultrasonic transducers
    - Measures flow rate with sound waves.
    - High precision without reducing pipe diameter
    - Low maintenance cost, no moving parts.
  • Piston and calometric principle
    - Piston or heat sensor reacts to the flow.
    - High precision, suitable for laboratories and sensitive processes.
  • Electromagnetic sensors
    - Measurement principle based on magnetic fields.
    - Ideal for conductive liquids.
    - Robust and chemically resistant.

Types of flowmeters

  • RFI series
    - Bucket flow meter in robust construction.
    - FDA-compliant material choice for drinking water.
    - Accurate measurements even in harsh industrial environments.
  • RM series (Hovercraft)
    - Measure both gases and liquids.
    - Flexible installation on panel or surface.
    - Suitable for medical equipment, laboratories and gas analysis.
  • VFA/VFB series (Visi-Float / float body)
    - Low-speed flows with visual readout.
    - Durable polycarbonate construction.
    - Ideal for laboratories and research applications.

 

 

FAQ - Frequently asked questions

What is the difference between a flow sensor and a flow meter?

  • A flow sensor measures the flow and sends an electrical signal to a control system, for example 4-20 mA, 0-10 V or pulse. A flow meter, on the other hand, displays the flow directly via a scale or visual indicator and is often used where local reading is needed.

 

What media can flow sensors and flow meters measure?

  • They can be used for both liquids and gases depending on the model. Common media are water, coolant, air, process fluids and other neutral gases or liquids.

 

Which type of flow measurement should I choose?

  • The choice depends on several factors such as flow range, medium, accuracy requirements and whether the signal is to be integrated into a control system. Turbine, rotor, float and electromagnetic flowmeters are some of the most common technologies.

 

Can flow sensors be used in industrial control systems?

  • Yes, many flow sensors are designed for integration into PLC and automation systems via analogue or digital signals. They are often used for process monitoring, alarms and flow control.

 

What should be considered when installing a flow sensor?

  • It is important to choose the right flow range, material compatible with the medium and correct installation in the pipework. In some cases, straight runs before and after the sensor are also required for optimal accuracy.

 

Which industries use flow sensors and flow meters?

  • They are used in many areas, such as industrial processes, water and wastewater systems, laboratory equipment, medical technology, cooling systems and OEM machinery.