DFM 6.1 Doppler Flow Meter

DFM 6.1 Doppler Flow Meter
Accurate non-contacting flow measurement of “difficult” fluids from outside a pipe




A Doppler flow meter is a type of ultrasonic flow meter. These devices use a scientific principle called the Doppler effect to measure the volumetric flow through a pipe. This works in such a way that the Doppler flow meter is clamped onto the outside of the pipe, so that it does not disrupt flow, as is required for other types of flow meter.
Doppler flow meters use the frequency of an ultrasonic beam to determine the flow rate of a liquid. This measurement is possible because of the Doppler effect, discovered by the Austrian scientist Christian Johann Doppler in the early 1800s. Essentially, the Doppler effect states that the frequency of sound waves varies depending on the movement of the receiver of the sound, or the source of the sound relative to the medium that the sound travels in. In this case, the medium that the wave travels in is the liquid flowing through the pipe.
For a Doppler flow meter to work properly, the liquid must contain particles or bubbles, so one works well for dirty liquids but is not very effective for clean water. The flow meter transmits an ultrasonic signal, and the signal is reflected by the particles and bubbles, which causes the frequency of the signal to shift. This frequency shift is what is measured by the flow meter.Gaining accurate flow measurement inside a pipe can sometimes be tricky. The Greyline DFM 6.1 Doppler Flow Meter offers clamp-on pipe flow measurement from outside the pipe. Its Doppler technology makes it perfect for ‘difficult’ liquids, or liquids with suspended solids such as wastewater, slurries, sludge, chemicals, viscous liquids, and abrasives. The non-invasive Doppler flow meter fits any pipe 12.5 mm (0.5 in) inside diameter or larger and clamps on the outside, gaining flow measurement readings without interrupting the process.

The DFM 6.1’s easy-to-follow, 5-button menu keypad makes setting up parameters of the flow application quick and easy and works on the majority of pipe materials. The Doppler technology sends a signal through the pipe wall and is reflected off the particles within the liquid, the change in frequency is reflected on the controller in the form of pipe flow measurement.
Use Doppler pipe flow measurement to control flow within a process, protect pumps from no-flow or dry pumping, or for flow proportionate use – you can even use it to test existing equipment to ensure it’s still providing accurate pipe flow measurement.

  1. Enhanced Performance
  2. Easy to Install and Configure
  3. Non-Contacting Clamp-On Ultrasonic Sensor
  4. Works on a Large Variety of Pipe Materials and Sizes
  5. Large Back-lit Flow Rate Display and Totalizer
  6. Isolated 4-20mA Output
  7. 2 Programmable Control Relays
  8. Optional MODBUS®RTU or HART Output
  9. 128MB Data Logger (26 million points)


General Specifications
Spec name: Description:
Flow Rate Range ± 0.03 m/s to 12.2 m/s (± 0.1 ft/s to 40 ft/s) in most applications
Pipe Size Any pipe ID from 12.7 mm to 4.5 m (0.5 in to 180 in)
Accuracy ±2% of reading or 0.03 m/s (0.1 ft/s) whichever is greater. Requires solids or bubbles minimum size of 100 microns, minimum concentration 75 ppm.
Repeatability: ±0.1%, Linearity ±0.5%
Display White, backlit matrix – displays flow rate, relay states, 16-digit totalizer, operating mode, and calibration menu
Configuration Built-in 5-button keypad with English, French, or Spanish language selection
Power Input 100-240 V AC 50/60 Hz, 10 VA maximum
Optional: 9-32 V DC, 10 W maximum
Output Isolated 4-20mA (1000 ohm load max.) or 0-5 V DC (field selectable)
Control Relays Qty 2, rated 5 amp SPDT, programmable flow alarm, and/or proportional pulse
Data Logger Built-in 26 million point logger with a USB output and Windows software
Enclosure Heater NEMA4X (IP 66) polyester with a clear polycarbonate face
Operating Temperature (Electronics) -23 °C to 60 °C (-10 °F to 140 °F)
Shipping Weight 6.3 kg (14 lbs)
Sensor Specifications
Spec name: Description:
Model SE4 Single-head ultrasonic with 7.6 m (25 ft) shielded cable and stainless steel mounting kit for pipes 12.7 mm (0.5 in) ID or larger.
Designed to withstand accidental submersion to 10 psi. Certified non-incendive for Class I Division 2, Groups A, B, C, D hazardous locations
Operating Temperature -40 °C to 150 °C (-40 °F to 300 °F)
Exposed Materials 316SS


Options: Description:
Sensors Intrinsic safety barriers for installation in Class I, Div 1, Groups C, D; Class II, Groups E, F, G; Class III; Encl. Type 4 hazardous locations.
Industrial Automation Protocols Modbus RTU via RS-485 or HART (field selectable)
Sensor Cable 15 m (50 ft) or 30 m (100 ft) continuous shielded coaxial pair, or splice up to 500 ft (152 m) with junction box. Self tunes to extended cable.
Enclosure Heater For outdoor installation, thermostatically controlled to -40 °C (-40 °F)
Control Relays 4 additional (6 total) rated 5 A SPDT


  • JB2X Sensor Cable Junction Box: Sensor cable junction box, NEMA4X/IP66 polycarbonate
  • PM Flange Assembly: Panel mount flange assembly for the Greyline flow meters
  • DXC Sensor Cable: Extra sensor cable up to 500 ft/150 m (RG174U shielded coaxial pair)
  • SE4-A Sensor: Replacement sensors with up to 100 ft/30m of continuous cable



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