DFM-IV Doppler Flow Meter
  • Non-Contacting Ultrasonic Sensor
  • Large, 4-Digit LCD Display
  • 10-Digit Totalizer
  • Isolated 4-20mA (1000 ohm)
  • 3 Programmable Control Relays
  • Adjustable Sensitivity
  • Intrinsically Safe Sensor Option
  • Built-in 3-Key Calibrator
  • RFI Rejection Filters

Measure flow from outside a pipe. The Greyline DFM-IV is ideal for "difficult liquids" that would damage regular flow meters - wastewater, slurries, sludge, chemicals, viscous liquids and abrasives. There is no obstruction to flow and no pressure drop. The standard, strap-on ultrasonic sensor fits any pipe 1/2" (12.5 mm) Inside Diameter or larger. The electronics/display enclosure can be mounted nearby.

Use the isolated 4-20mA to transmit flow to remote displays, recorders or controllers. The 3 programmable relays can be used for flow control, pump protection or flow proportionate pulse. Calibration is easy with the built-in 3-key calibrator. Display and totalize flow in your choice of engineering units (gallons, liters etc.)

Sensor cable can be extended up to 500 ft. (152 m) with no loss of signal. The DFM-IV can be equipped with intrinsic safety barriers for sensor installation in hazardous rated locations. Other options include high temperature sensors and a built-in 50,000 point Data Logger.

Standard features include:

  • sensor - strap-on, single head ultrasonic for 1/2" to 180" (12.5 mm to 4.5 m) ID pipes
  • sensor cable - 20ft / 6m shielded coaxial pair
  • installation - sensor compound kit - PC3 stainless steel sensor mounting clamp
  • enclosure - watertight NEMA4X (IP66) polycarbonate
  • displays - Flow Rate - large 4-digit LCD - Totalizer/Menu/Status - 16-digit alphanumeric
  • calibration - built-in 3-key programmer
  • sensitivity - keypad adjustable
  • output - Isolated 4-20mA (1000 ohm)
  • 3 control relays - 5 amp SPDT - programmable for flow proportional pulse output, and/or flow alarm
  • backflow rejection - external, voltage-free relay input
  • electrical surge protection and RFI filters: AC line, sensor, 4-20mA
  • power input - 100-130VAC 50/60Hz
  • 1 Manual - Installation and Operation


SCOPE: This specification covers a non-intrusive, ultrasonic Doppler-type flow meter as manufactured by Greyline Instruments Inc., Massena, New York / Long Sault, Ontario. The instrument shall provide for velocity or volumetric indicating and transmitting of the flow rate in a full pipe.


  1. The flow meter shall operate with a single-head flow sensor mounted externally on any contiguous pipe material that conducts sound including: carbon steel, stainless steel, ductile iron, copper, FRP, PVC, ABS, or cement lined pipe from 1/2" to 180" (12.5 mm to 4.5 m) ID.
  2. Measure and indicate flow rates between 0.2 to 40 ft/sec (0.06 to 12.2 m/sec) with accuracy of 2% of full scale on liquids with entrained particles or gases of 100 microns or larger and minimum concentrations of 75 ppm.


  1. The flow sensor shall be single-head, ultrasonic in a stainless steel housing. It shall be installed on the outside of a pipe without interrupting flow. The sensor shall be capable of continuous operation at temperatures from -40F to 200F (-40C to 93C), and to withstand accidental submersion pressures to 10 psi.
  2. Shall include Manufacturer's recommended sensor coupling compound and adjustable stainless steel sensor mounting clamp.
  3. Shall include 20 ft (6m) Sensor cable, shielded coaxial pair.
  4. Shall be capable of extending sensor cable up to 500 ft (152m), without adjustment, and with no reduction in performance or signal strength.
  5. Shall be transformer isolated and designed to meet intrinsic-safe requirements. Shall be designed for maximum RFI rejection, and include automatic high voltage bleeds for nearby lightning strikes.


  1. The transmitter-indicator shall be housed in a watertight and dust tight NEMA4X (IP 66) polycarbonate enclosure with a gasketed shatter proof window, and suitable for wall mounting. Mounting hardware shall be included.
  2. Flowmeter electronics shall be designed to operate at temperatures from -5 to 140F (-20 to 60C). Electronic circuits are interchangeable with other flowmeters having the same model number. The transmitter circuit and calibration frequency standard shall be crystal controlled. The transmitter shall be powered by 100-130VAC 50/60Hz requiring less than 5 watts.
  3. The transmitter shall include a built-in 3-Key calibration system with operator selection of parameters through visual prompts from a Menu calibration system. Systems requiring calibration by Parameter codes, BCD switches or external calibrators shall not be accepted.
  4. The 4-20mA shall be flow proportional and isolated, with programmable zero and full scale offsets. Maximum resistive load shall be 1000 ohms. It shall include automatic high voltage bleeds for nearby lightning strikes.
  5. Shall include noise suppression circuitry to filter electrical interference.
  6. Have a continuous 4-digit LCD display indicating flow in user-selected engineering units. Have a 16-digit alphanumeric display indicating totalized flow, units of calibration, and/or signal strength.
  7. The transmitter shall contain electronic means to prevent cross-talk from other in-service flow meters from the same manufacturer.
  8. Have 3 control relays rated 5 ampere SPDT. Relays shall be programmable for flow proportional pulse output, or as flow rate alarms with separate ON/OFF set points.
  9. Have circuitry to force the flowmeter outputs and display to zero during backflow conditions by sensing a voltage-free contact closure from a remote relay device.


  1. Sensor, connecting cable and junction boxes shall be rated intrinsically safe to Class I,II,III, Div. I,II, Groups C,D,E,F,G.
  2. Sensor cable shall be 50 ft (15m) length shielded coaxial pair.
  3. Have a Cable Junction Box and up to 500 ft (152m) extra Sensor cable that shall be shielded coaxial pair installed in conduit for mechanical protection.
  4. Have a High Temperature Sensor for operating temperatures from -40 to 302F (-40 to 150C)
  5. Have a thermostatically controlled enclosure heater for condensation protection in locations with temperature below -5F (-20C).
  6. Have power input of 200-260VAC 50/60Hz, or 24VDC, or 12VDC.
  7. Have a built-in 50,000 point Data Logger with RS232C output. Have serial cable for data transfer to a PC computer, and Windows software for data transfer.


The Flow Meter shall be a Model DFM-IV Doppler Flow Meter as manufactured by Greyline Instruments Inc., and warranted against defects in materials and workmanship for one year.