SPX Thermal Flow Switch

Thermal Flow Switch
SPX Thermal Dispersion Flow Switch

The SP series thermal dispersion flow switch is a solidstate flow switch with no moving parts. It can be used for monitoring flow/no-flow conditions of a very wide range of liquids. The SP thermal dispersion flow switch can be provided with solidstate or relay output. They are relatively compact and can be applied in a range of pipe sizes. Available in a variety of process connection sizes, choices of lengths, and materials of construction to meet a wide range of application requirements. It is also available for general purpose and explosionproof environments.

The SPX Thermal dispersion flow switches measure the velocity of a liquid inside a pipe or channel. The switch’s probe contains two key components – a heating sensor and temperature sensor. The heating sensor is positioned closest to the flowing liquid and provides a consistent heat. The temperature sensor measures the temperature emitted from the heating sensor.

When liquid is flowing, there is a temperature difference between the two sensors. The temperature difference has an inverse relationship with the flow velocity (fast flowing liquids will result in greater heat differences and vice versa).

The SPX Flow Switch is a reliable and accurate flow switch and since the device contains no moving parts, it has no wear and tear and maintains a long lifespan.


Thermal flow switches have many uses in many applications across many industries. Food, Beverage, Drinking Water, Edible Oil, Food Process Filling, Pharmaceutical, High Temperature Disinfection, Petrochemicals, Hydroelectric plants, Shipyard, HVAC Systems, Steel Industry, Pharmaceutical, Semiconductor Industry, Cooling pipes flow control and any pipes carrying liquid where flow measurement is needed.

  • High sensitivity and accuracy.
  • Suitable for liquid application with impurities.
  • Suitable for corrosive and hazardous conditions.
  • Can be calibrated for liquids with different densities and impurities.
  • Suitable for complex locations with easy installation.
  • Customized probe lengths available to meet a variety of applications.
  • Three different output signals options.
  • Different materials on request for food / food additives application.

Measuring Range: Water: 1~150 cm/s; Oil: 3~300 cm/s

Flow velocity: Switching point 50cm/s @25C, Water

Operating Voltage: 19 ~ 30Vdc

Process Temperature: -20 ~ 80C

Operating Pressure: 100 bar (max.)

Output: Open Collector : NPN / PNP(<400mA) or Relay : 1A/30Vdc, 0.3A/125Vac (NO or NC)