DFS 5.1 Doppler Flow Switch

  • Easy Mounting, Single Head Sensor
    12.5mm up to 4500mm 
  • Wide Flow Rate
    Velocity: +/-0.076 - 3 m/s
  • Sensor Cable Length
    Up to 152 meters.
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Flow switch with non-contacting sensor control flow from outside a pipe. Recommended for "difficult liquids" including wastewater, cooling water, slurries, sludge, chemicals, viscous liquids and abrasives. The Greyline DFS 5.1 is ideal for pump protection or to activate flow/no-flow alarms.

Easy to calibrate

The DFS 5.1 control relay can be set to turn ON and OFF at any flow rate between 0.25 and 10 ft./sec (0.075 to 3 m/sec). Insert two links for separate ON/OFF set points or just one link for a High or Low flow alarm. Set the relay actuation time delay from 0 to 80 seconds.

A bright LED indicator shows the relay state and a LED bar graph shows the flow rate. Electronics are housed in a watertight polycarbonate wall-mount enclosure.

The clamp-on ultrasonic sensor mounts on the outside of metal or plastic pipes without cutting the pipe or shutting down flow. It works on any pipe diameter 1/2" (12.5 mm) or larger and installs in minutes. There are no moving parts and no maintenance is required. The shielded sensor cable length is 20 ft. (6 m) and can be extended up to 500 ft. (152 m) with an optional Junction Box.

General Specification
Transmitter Enclosure 

Watertight, dust tight NEMA4X (IP 67) polycarbonate with a clear shatter-proof face

Transmitter operating temperature: -23°C to +60°C
Control Relay 5 Amp. DPDT
Accuracy Up to 2%
Repeatability  0.1%
Indication Flow rate LED bargraph, Relay status LED
Sensor Specification
Pipe diameters range:

12.5 up to 4500mm

Senosor housing material Stainless steel
Operating temperature: -40°C to +150°C
Accidental submersion Pressure up to 10 psi





Viscous liquids


Caustics and abrasives