SP Series is a thermal dispersion flow switch is a precise flow sensing device for liquids. The principle of operation is based on heat transfer. The SP thermal dispersion flow switch is offered with a variety of output types and materials of construction. No moving parts make the SP series a long lasting and high value flow switch. 


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). Since the device contains no moving parts, has no wear and tear and maintains a long lifespan.

Thermal Dispersion Flow Switch

    • No moving parts, solidstate performance and reliability
    • 1~59″ per second (150cm/s) measuring range for water; 1~118″ (300cm/s) range in oil
    • 304SS, 316SS, PVDF and polypropylene wetted parts
    • Maximum operating pressure up to 1,450psi (100bar)
    • Choice of NPN/PNP, N.O. or N.C. relay, or SPDT relay output
    • Standard and custom extended insertion lengths
    • Standard or high temperature, explosionproof units available
    • LED indication of flow status
    • Marine certified unit available
  • USE

    • Detect positive flow to control downstream process
    • Ensure machinery safe operation with detection of coolant flow


    • HVAC
    • Petrochemical
    • Power
    • Food processing
    • Pharmaceutical
    • Many others