Greyline AVFM 6.1 Area-Velocity Flow Meter

 Measure flow through partially filled pipes, channels, canals, and turnouts without a flume or weir. The AVFM 6.1 uses a submerged ultrasonic sensor to continuously measure both Velocity and Level in the channel. The sensor resists fouling, corrosion and abrasion.

The flow meter can be configured with the standard submerged velocity-level sensor or with submerged velocity plus a separate non-contacting ultrasonic level sensor, for highly aerated fluids or those with high concentration of suspended solids.

View flow rate and total flow on the large backlit LCD display and connect to external devices with three 4-20mA outputs and two control relays. Flow rate, volume, run hours, and diagnostic information available through the optional Modbus RTU serial communications.



  • No flume or weir required - Submersible ultrasonic sensor measures velocity and level simultaneously to calculate flow, no moving parts to wear, foul or clog.
  • Built in 5 button keypad - intuitive menu, and large backlit LCD display make the AVFM 6.1 the most operator-friendly area velocity flow meter on the market.
  • Fast, simple, installation and setup.
  • Improved performance in a wider range of operating conditions.
  • View flow rate, velocity, level, totalizer, relay status, and important diagnostic information on the LCD display.
  • Three isolated 4-20mA outputs for flow rate, velocity, and level, and two relay outputs for pulse output or alarm.
  • 6.5 million point data logger for greater flexibility of data monitoring, control, and reporting.
  • Min, Max, and Total Flow data from the last 365 days is available on the LCD display, or download directly to a USB for easy reporting.
  • Monitors flow rate, volume total, run hours, and diagnostic information through only two wires with the optional Modbus RTU serial communication output.


  • Stormwater
  • Wastewater
  • Irrigation Water
  • Effluent
  • Industrial Wastewater


General Specifications

  • Channel Types: Round pipe, rectangular, trapezoid, egg or custom shapes
    Electronics Enclosure: Watertight and dust tight NEMA4X (IP 66) polycarbonate with clear, shatterproof cover
  • Accuracy: Level: ±0.25% of reading or ±0.08”, whichever is greater. Repeatability & Linearity 0.1%. Velocity: ±2% of reading or ±0.04 ft/sec, whichever is greater. Requires solids or bubbles minimum size of 100 microns, minimum concentration 75ppm. Repeatability & Linearity 0.5%
  • Display: White, back-lit matrix - displays flow rate, totalizer, relay states, operating mode and calibration menu
  • Programming: Built-in 5-key calibrator with English, French or Spanish language selection
  • Power input: 100-240VAC 50-60Hz, 10VA maximum. Optional: 9-32VDC, 10 WATTS maximum
  • Outputs: 3 Isolated 4-20mA, 1000 ohm, (Flow, Level and Velocity) or 0-5VDC by menu selection
  • Control relays: 2 Relays, form 'C' dry contacts rated 5 amp SPDT;
  • Data logging: programmable for flow proportional pulse (sampler/totalizer), flow and/or level alarm Programmable 26 million point data capacity, time and date stamped plus formatted flow reports including Total, Average, Minimum, Maximum and times of occurrence. Includes USB output to Flash Drives and Windows software
  • Operating Temp. (electronics): -5° to 140°F (-20° to 60°C)
  • Approximate Shipping Weight: 10 Lbs. (4.5 Kg)
  • Approvals: CE, CSA/UL/EN 61010-1

QZ02L Sensor

  • Velocity Measurement Range: 0.1 to 20 ft/sec (0.03 to 6.2 m/sec) and reverse flow to -5 ft/sec (-1.5 m/sec) in fluids containing bubbles or solids with a minimum size of 100 microns and a minimum concentration of 75 ppm to act as acoustic reflectors
  • Level Measurement Range: Minimum Head: 1 in (25.4 mm). Maximum Head: 15 ft. (4.57 m)
  • Operating Temperature: 5 to 175°F (-15 to 80°C)
  • Exposed Materials: 316 stainless steel, epoxy resin, polyurethane
  • Sensor Cable: 25 Ft. (7.6 m) submersible polyurethane jacket, shielded, 3-coaxial
  • Sensor Mounting: Includes MB-QZ stainless steel mounting bracket
  • Temperature Compensation: Automatic, continuous


  • Industrial Automation Protocols: Modbus® RTU via RS-485
  • Sensor Cable: 50 ft. (15 m) or 100 ft. (30 m) submersible, continuous from Sensor - or splice up to total of 500 ft (150 m) length
  • Sensor Cable Junction Box: Watertight NEMA4 polycarbonate with connection terminal strip
  • Enclosure Heater: Thermostatically controlled to -40° F/C - recommended for temperatures below 32°F (0°C)
  • Intrinsic Safety Barriers: For Sensor mounting in Class I,II,III, Div. I,II, Groups C,D,E,F,G hazardous locations
  • Sensors: Separate non-contacting ultrasonic level sensor and submerged velocity sensor
  • Sensor Mounting Bands: Stainless steel sensor mounting bands for pipes 6” to 72” (150 to 1800 mm) diameter

Download Datasheet: Greyline AVFM 6.1 Area-Velocity Flow Meter

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