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WIKA FSD-4 Series Digital Flow Switch for Fluid, Liquid, 0.05 m/s Min, 3 m/s Max

WIKA FSD-4 Series Digital Flow Switch for Fluid, Liquid, 0.05 m/s Min, 3 m/s Max

RS Stock No. 269-0088

Brand WIKA

  • Category: Flow Sensors
  • Manufacturer: WIKA
  • Minimum Flow Rate: 0.05 m/s

€ 564.20

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SMC Flow Switch Series Digital Flow Switch Flow Switch for Dry Air, N2, 30 L/min Min, 3000 L/min Max

SMC Flow Switch Series Digital Flow Switch Flow Switch for Dry Air, N2, 30 L/min Min, 3000 L/min Max

RS Stock No. 281-0919

Brand SMC

  • Media Monitored: Dry Air, N2
  • Minimum Flow Rate: 30 L/min
  • Series: Flow Switch

€ 1.051.71

4 in stock now

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SMC PFM7 Series Digital Flow Switch Flow Switch, 0.2 l/min Min, 10 L/min Max

SMC PFM7 Series Digital Flow Switch Flow Switch, 0.2 l/min Min, 10 L/min Max

RS Stock No. 270-4301

Brand SMC

  • Category: Flow Sensors
  • Manufacturer: SMC
  • Supply Voltage: 24 V dc

€ 344.92

8 in stock now

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SMC PF2M7 Series Digital Flow Switch Flow Switch, 1 L/min Min, 100 L/min Max

SMC PF2M7 Series Digital Flow Switch Flow Switch, 1 L/min Min, 100 L/min Max

RS Stock No. 281-0917

Brand SMC

  • Brand: SMC
  • Maximum Flow Rate: 100 L/min
  • Minimum Flow Rate: 1 L/min

€ 295.43

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Endress+Hauser DTT31 Series Thermal Flow Switch Flow Switch for Liquid, 0.03 m/s Min, 3 m/s Max

Endress+Hauser DTT31 Series Thermal Flow Switch Flow Switch for Liquid, 0.03 m/s Min, 3 m/s Max

RS Stock No. 069-0253

Brand Endress+Hauser

  • Brand: Endress+Hauser
  • Category: Flow Sensors
  • Section: Automation & Control Gear

€ 441.76

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Endress+Hauser DTT31 Series Thermal Flow Switch Flow Switch for Liquid, 0.03 m/s Min, 3 m/s Max

Endress+Hauser DTT31 Series Thermal Flow Switch Flow Switch for Liquid, 0.03 m/s Min, 3 m/s Max

RS Stock No. 069-0254

Brand Endress+Hauser

  • Category: Flow Sensors
  • Section: Automation & Control Gear
  • Super Section: Sensors

€ 441.76

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Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.08 l/min Min, 0.53 L/min Max

Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.08 l/min Min, 0.53 L/min Max

RS Stock No. 250-8950

Brand Sensata / Cynergy3

  • Brand: Sensata / Cynergy3
  • Manufacturer: Sensata / Cynergy3
  • Super Section: Sensors

€ 38.33

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Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.07 l/min Min, 0.24 L/min Max

Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.07 l/min Min, 0.24 L/min Max

RS Stock No. 250-8951

Brand Sensata / Cynergy3

  • Maximum Flow Rate: 0.24 l/min
  • Media Monitored: Liquid
  • Supply Voltage: 240 V

€ 41.03

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Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.37 l/min Min, 0.99 L/min Max

Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.37 l/min Min, 0.99 L/min Max

RS Stock No. 250-8956

Brand Sensata / Cynergy3

  • Manufacturer: Sensata / Cynergy3
  • Media Monitored: Liquid
  • Super Section: Sensors

€ 39.68

7 in stock now

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Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.2 l/min Min, 0.47 L/min Max

Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.2 l/min Min, 0.47 L/min Max

RS Stock No. 250-8957

Brand Sensata / Cynergy3

  • Category: Flow Sensors
  • Device Type: Flow Switch
  • Super Section: Sensors

€ 42.40

1 in stock now

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SMC PF2A Series Digital Flow Switch Flow Switch for Air, 25 l/min Min, 525 L/min Max

SMC PF2A Series Digital Flow Switch Flow Switch for Air, 25 l/min Min, 525 L/min Max

RS Stock No. 270-4283

Brand SMC

  • Section: Automation & Control Gear
  • Series: PF2A
  • Supply Voltage: 12 → 24 V dc

€ 737.96

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SMC PF3W Series Digital Flow Switch for Water Flow Switch for Air, Gas, Water, 2 l/min Min, 16 L/min Max

SMC PF3W Series Digital Flow Switch for Water Flow Switch for Air, Gas, Water, 2 l/min Min, 16 L/min Max

RS Stock No. 270-4289

Brand SMC

  • Category: Flow Sensors
  • Manufacturer: SMC
  • Supply Voltage: 12 → 24 V dc

€ 825.58

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SMC PF3W Series Digital Flow Switch for Water Flow Switch for Air, Gas, Water, 5 l/min Min, 40 L/min Max

SMC PF3W Series Digital Flow Switch for Water Flow Switch for Air, Gas, Water, 5 l/min Min, 40 L/min Max

RS Stock No. 270-4292

Brand SMC

  • Manufacturer: SMC
  • Media Monitored: Air, Gas, Water
  • Section: Automation & Control Gear

€ 821.58

5 in stock now

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SMC PFMB7 Series Digital Flow Switch Flow Switch for Dry Air, N2, 5 L/min Min, 500 L/min Max

SMC PFMB7 Series Digital Flow Switch Flow Switch for Dry Air, N2, 5 L/min Min, 500 L/min Max

RS Stock No. 281-0924

Brand SMC

  • Device Type: Digital Flow Switch
  • Distrelec Product Id: 11073988
  • Supply Voltage: 12 → 24 V dc

€ 376.39

3 in stock now

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Endress+Hauser DTT31 Series Thermal Flow Switch Flow Switch for Liquid, 0.03 m/s Min, 3 m/s Max

Endress+Hauser DTT31 Series Thermal Flow Switch Flow Switch for Liquid, 0.03 m/s Min, 3 m/s Max

RS Stock No. 069-0255

Brand Endress+Hauser

  • Brand: Endress+Hauser
  • Section: Automation & Control Gear
  • Super Section: Sensors

€ 441.76

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Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.37 l/min Min, 0.99 L/min Max

Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.37 l/min Min, 0.99 L/min Max

RS Stock No. 250-8952

Brand Sensata / Cynergy3

  • Category: Flow Sensors
  • Manufacturer: Sensata / Cynergy3
  • Supply Voltage: 240 V

€ 39.68

7 in stock now

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Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.2 l/min Min, 0.47 L/min Max

Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.2 l/min Min, 0.47 L/min Max

RS Stock No. 250-8953

Brand Sensata / Cynergy3

  • Brand: Sensata / Cynergy3
  • Device Type: Flow Switch
  • Minimum Flow Rate: 0.2 L/min

€ 42.40

4 in stock now

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Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.08 l/min Min, 0.53 L/min Max

Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.08 l/min Min, 0.53 L/min Max

RS Stock No. 250-8954

Brand Sensata / Cynergy3

  • Brand: Sensata / Cynergy3
  • Category: Flow Sensors
  • Manufacturer: Sensata / Cynergy3

€ 38.33

1 in stock now

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Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.07 l/min Min, 0.24 L/min Max

Sensata / Cynergy3 Sensata Cynergy3 FSU Series Flow Switch Flow Switch for Liquid, 0.07 l/min Min, 0.24 L/min Max

RS Stock No. 250-8955

Brand Sensata / Cynergy3

  • Category: Flow Sensors
  • Minimum Flow Rate: 0.07 L/min
  • Series: FSU

€ 41.03

2 in stock now

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SMC IFW5 Series Flow Switch Flow Switch for Air, Gas, Liquid, Water, 1 l/min Min, 10 L/min Max

SMC IFW5 Series Flow Switch Flow Switch for Air, Gas, Liquid, Water, 1 l/min Min, 10 L/min Max

RS Stock No. 270-2876

Brand SMC

  • Device Type: Flow Switch
  • Manufacturer: SMC
  • Supply Voltage: 24 V dc

€ 231.58

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SMC PF2A Series Digital Flow Switch Flow Switch for Air, 2.5 l/min Min, 52.5 L/min Max

SMC PF2A Series Digital Flow Switch Flow Switch for Air, 2.5 l/min Min, 52.5 L/min Max

RS Stock No. 270-4282

Brand SMC

  • Device Type: Digital Flow Switch
  • Maximum Flow Rate: 52.5 L/min
  • Series: PF2A

€ 703.49

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SMC PF2W Series Digital Flow Switch Flow Switch for Water, 2 L/min Min, 16 L/min Max

SMC PF2W Series Digital Flow Switch Flow Switch for Water, 2 L/min Min, 16 L/min Max

RS Stock No. 281-0918

Brand SMC

  • Media Monitored: Water
  • Minimum Flow Rate: 2 L/min
  • Supply Voltage: 12 → 24 V dc

€ 759.96

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SMC PF3A712H Series Digital Flow Switch Flow Switch for Dry Air, N2, 120 L/min Min, 12000 L/min Max

SMC PF3A712H Series Digital Flow Switch Flow Switch for Dry Air, N2, 120 L/min Min, 12000 L/min Max

RS Stock No. 281-0920

Brand SMC

  • Section: Automation & Control Gear
  • Super Section: Sensors
  • Supply Voltage: 24 V dc

€ 1.245.74

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SMC PF3W Series Digital Flow Switch Flow Switch for Water, 2 L/min Min, 16 L/min Max

SMC PF3W Series Digital Flow Switch Flow Switch for Water, 2 L/min Min, 16 L/min Max

RS Stock No. 281-0921

Brand SMC

  • Maximum Flow Rate: 16 L/min
  • Minimum Flow Rate: 2 L/min
  • Series: PF3W

€ 691.58

4 in stock now

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...

What is a flow switch?
A flow switch is a sensor that monitors the movement of liquids or gases through a pipe or duct and generates a signal when the flow rate crosses a preset threshold. This can be used to start or stop pumps, control valves, or interlock processes to protect equipment and optimize efficiency. Flow switches come in several designs, including paddle-type (flow pushes a paddle to actuate contacts), turbine-type (a small impeller detects flow), and differential-pressure types (pressure drop across a restriction triggers a switch). They are commonly used in HVAC, plumbing, water treatment, and industrial automation.

How does a flow switch work?
A flow switch typically uses a mechanical or electrical sensing element to detect moving fluid and translate that into an electrical output. In paddle or turbine models, the moving fluid pushes a sensor or wheel, which then moves a contact from one state to another (normally open or normally closed). In differential-pressure types, a pressure drop across a flow element converts fluid motion into a measurable pressure difference that drives a switch. The result is a controllable signal that can shut off a pump, start another device, or trigger a alarm. Some models feature adjustable setpoints, hysteresis, and multiple output configurations (NO, NC, or changeover) to suit complex control schemes.

What are the main types of flow switches?
Flow switches come in several common configurations, each suited to different installations and fluids:
  • Paddle (or vane) flow switch: A flat paddle or vane is pushed by the flowing fluid to actuate a switch. Ideal for clean liquids and straightforward installation.
  • Turbine (or impeller) flow switch: An inline turbine spins with the flow; rotation triggers the switch. Suitable for higher flow rates and precise control.
  • Differential-pressure flow switch: A restriction creates a pressure difference that is monitored by a sensor; changes in flow alter the differential pressure and switch state.
  • Magnetic or reed switch flow switch: A magnetically actuated sensor detects flow without direct contact, useful in sanitary or low-leakage applications.
  • Ultrasonic or thermal flow switches (less common as discrete options): Use flow-induced changes in transit time, density, or heat transfer for switching in special environments.

Where are flow switches used?
Flow switches are versatile for both safety interlocks and control loops across many industries:
  • HVAC systems to start/stop circulation pumps based on differential flow in heating or cooling loops
  • Water treatment and filtration plants for pump protection and backflow prevention
  • Industrial automation lines where process sequences depend on fluid movement
  • Plumbing systems to guard against dry-running of pumps
  • Chemical processing and pharmaceutical manufacture where sanitary, compliant sensing is required
  • Food and beverage processing where clean-in-place (CIP) compatibility is important
  • Oil and gas, petrochemical, and power generation applications with robust environmental ratings

How do I choose the right flow switch?
Selecting the right flow switch involves matching the device to your process, pipe size, and media. Consider:
  • Ensure the switch activates at the operational flow rate required by the control system.
  • Materials (stainless steel, PVC, brass), seals, and coatings must resist the process fluid (water, oil, chemicals, slurry).
  • Choose ratings that exceed process conditions to avoid failure.
  • Output type (NO/NC, changeover), contact rating, and supply voltage must match the controller or PLC.
  • Straight-run length, presence of elbows, and accessibility for maintenance.
  • For outdoor or hazardous environments, select appropriate enclosure protection (IP ratings) and certifications (CE, RoHS, ATEX/IECEx if applicable).
  • Some switches require periodic calibration or cleaning, especially paddle and turbine types in dirty systems.

How do I install and wire a flow switch?
Installation and wiring vary by model, but general guidelines help ensure reliable operation:
  • Turn off power to the control circuit and depressurize the line before installation.
  • Install in a straight section of pipe with adequate straight-run distance before and after the sensor to avoid turbulence.
  • Choose the correct orientation and connection type (threaded, flanged, or compression) for your piping system.
  • Use appropriate gaskets, seals, and torque specifications to prevent leaks or motion-induced wear.
  • Connect the output to the correct input on the control system or PLC, observing NO/NC configuration and any required pull-up or pull-down resistors.
  • Verify electrical ratings, supply voltage, and safety certifications; if the switch is explosion-proof or weather-proof, ensure proper enclosure is used.
  • Once mounted, test with a known flow condition and confirm that the controller responds as intended, adjusting setpoints if available.

How do I troubleshoot a flow switch that isn’t responding?
Troubleshooting steps help identify common causes of non-responsiveness:
  • Check power and wiring: confirm supply, correct grounding, and that the control inputs match the switch output (NO/NC).
  • Inspect the sensing element: paddle or turbine can jam with debris, scale, or sediment; clean or replace if necessary.
  • Verify setpoint and hysteresis: ensure the adjustable range aligns with the actual flow in the system.
  • Look for leaks or incorrect installation: misalignment or air ingress can affect readings, especially in differential-pressure switches.
  • Test with a simulated flow source: bypass or temporarily increase flow to confirm switch activation.
  • Check for electrical interference or wiring damage that could mask signals or trigger spurious outputs.
  • Ensure the media temperature and chemical compatibility have not degraded seals or sensor components.

What maintenance and replacement considerations apply to flow switches?
Regular maintenance extends the service life and reliability of flow switches:
  • Periodic cleaning of the sensing element to prevent buildup that reduces sensitivity.
  • Inspection of seals, gaskets, and enclosure integrity to maintain IP/ATEX ratings where required.
  • Calibration checks and, if available, recalibration according to the manufacturer’s schedule or process requirements.
  • Replacement of worn or damaged parts, such as paddle blades, impellers, or reed contacts, to preserve accurate switching.
  • Verification of electrical connections and corrosion-resistant fittings in aggressive environments.
  • Documentation of changes for process history and quality standards in regulated industries.

What related components should I consider with a flow switch?
Flow switches are often part of a broader instrumentation and control package. Consider these compatible components:
  • Flow meters and flow sensors for precise measurement alongside switching actions
  • Differential-pressure transmitters and pressure switches for multi-point control
  • Valves, actuators, and pumps with compatible electrical interfaces
  • Filters, strainers, and strainers upstream to protect the sensing element
  • Tubing, fittings, and seals designed for the process fluid and temperature
  • Control relays, PLCs, and safety interlocks with appropriate input ratings
  • Sanitary and hygienic versions for food, beverage, or pharmaceutical lines

Are flow switches suitable for hazardous environments or special certifications?
Yes, many flow switches are designed for demanding applications and offer certifications for specific environments:
  • Explosion-proof or intrinsically safe variants for hazardous areas
  • ATEX and IECEx certifications where required by local regulations
  • IP65/IP66 or higher ingress protection for washdown and outdoor installations
  • Materials compatible with aggressive chemicals or high-temperature media
  • Compliance with industry standards such as CE, UL, CSA, RoHS, and REACH

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