Greyline Instruments Inc.

- Model AVFM 5.0 - Area-Velocity Flow Monitor



Monitor flow through open channels, partially full sewer pipes and surcharged pipes without a flume or weir. Ideal for stormwater, combined effluent, raw sewage, irrigation water and streams. Calibration is simple: enter the pipe diameter or channel shape and the AVFM 5.0 computes the flow volume and displays the flow rate. Measure forward and reverse flow and calibrate to channels of any shape.


The AVFM 5.0 uses a submerged ultrasonic sensor to measure both Velocity and Level in the channel. The sensor is completely sealed with no orifices or ports. It mounts inside a pipe or at the bottom of a channel.

Area-Velocity Flow

Measure open channel flow without a flume or weir
An Area-Velocity Flow Meter continuously measures both Level and Velocity to calculate flow volume in an open channel or pipe.

The ultrasonic sensor is installed at the bottom of a pipe or channel. To measure water level the sensor transmits ultrasonic pulses that travel through the water and reflect off the liquid surface. The instrument precisely measures the time it takes for echoes to return to the sensor. Based on the speed of sound in water, the level is measured with accuracy of ±0.25%.

Flow velocity is measured with an ultrasonic Doppler signal continuously injected into the water. This high frequency sound (640 KHz) is reflected back to the sensor from particles or bubbles suspended in the liquid. If the fluid is in motion, the echoes return at an altered frequency proportionate to flow velocity. With this technique the instrument measures flow velocity with accuracy of ±2%.

Greyline Area-Velocity Flow Meters work in partially full and surcharged pipes, rectangular, trapezoid and egg-shaped channels.

Optional - Separate Level and Velocity Sensors
A separate down-looking ultrasonic sensor can be used for highly aerated or turbulent flow applications. It measures level by transmitting ultrasonic pulses through the air to the liquid surface with accuracy of ±0.25%. Along with the level sensor, a submerged Doppler velocity sensor is used to measure the water velocity.

  • For Open Channels and Pipes No Flume or Weir Required
  • Ultrasonic - Measures Velocity + Level to Calculate Flow
  • Works in partially filled and surcharged pipes
  • Measures Forward and Reverse Flow
  • 3 Isolated 4-20mA Outputs (Flow, Level and Velocity)
  • Totalizer and 2 Control Relays
  • Optional Intrinsically Safe Sensor
  • Optional built-in 2-million point Data Logger

The AVFM 5.0 is recommended for pipe diameters greater than 6' (150 mm). Maximum pipe diameter or channel width should not exceed 10 ft (3 m) unless flow velocity is evenly distributed across the channel width. Avoid sensor mounting locations where sediment builds up and locations where there is an elevation drop or bend immediately upstream from the sensor. Maximum pipe or channel slope should not exceed 3%.

The AVFM 5.0 measures flow velocity from 0.1 to 20 ft/sec (0.03 to 6.2 m/sec) and reverse flow up to 5 ft/sec (1.5 m/sec).

Submerged Sensor Measures Level And Velocity

Do it the easy way - use a stainless steel pipe band for Area-Velocity Flow Meter sensor mounting. You can install the sensor and tie wrap the cable in place before you enter the manhole. Then insert the pipe band into the manhole inlet pipe and tighten the scissor-jack to expand the band for a friction fit inside the pipe.

Pipe Mounting Bands are available from Greyline in a range of sizes for common pipe diameters.

Easy to Use
The AVFM 5.0 Area-Velocity Flow Meter measures both Level and Velocity to calculate flow in an open channel or pipe. Calibration is simple: enter the pipe diameter or channel dimensions and the AVFM 5.0 automatically computes and displays flow volume.

The ultrasonic sensor mounts inside the pipe or on the bottom of a channel with a stainless steel mounting bracket (included) and a single screw into the bottom of the pipe or channel. No special compounds, tools or hardware are required. The sensor is completely sealed with no orifices or ports.

Recommended Pipe or Channel Conditions
Careful selection of sensor mounting location results in best performance and maintenance-free operation. Avoid locations where sediment builds up.

Best possible accuracy will result when the water is not highly turbulent and where velocity is evenly distributed across the channel. The channel should not have drops or direction changes immediately upstream of the sensor mounting location. Pipe or channel slope should not ex|seed 3%.

The AVFM 5.0 can measure forward flow velocity up to 20 ft/sec (6 m/sec) and reverse flow up to 5 ft/sec (1.5 m/sec). The electronics and software sample and average flow rates continuously to provide stable readings. The submerged velocity/level sensor will measure flow in partially full and surcharged pipes with pressure up to 10 psi. No special set-up or adjustment is required. Minimum recommended pipe diameter is 6' (150 mm).


The standard sensor measures both velocity and level with a single submerged probe. It is installed in the pipe or channel floor with the stainless steel mounting bracket (supplied), or mounted with an optional stainless steel band for round pipes. Alternate sensor models are available for special applications: a separate non-contacting ultrasonic level sensor with a submerged velocity sensor. Sensor cable can be extended up to 500 ft (150 m).


Calibrate the AVFM 5.0 for installation in irregular or compound channel shapes by entering the channel width at multiple level points through a . Channels of virtually any shape can be monitored with your choice of measurement units.


Choose the built-in data logger option if you want the AVFM 5.0 to store time and date-stamped flow values at 10 second to 60 minute intervals. Daily flow reports are automatically created where total, minimum, maximum and average flow rates are displayed on the LCD display. Transfer log files to any USB flash drive just by connecting to the logger's USB output. Windows software is included to display log files in graph and table formats, change measurement units and generate flow reports. Export data to to graphic or text file formats, or directly to Microsoft Excel.

General Specifications: Greyline AVFM 5.0 Area-Velocity Flow Monitor

  • 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 Range. Velocity: ±2% of Reading. Repeatability and Linearity: ±0.1%
  • Display: White, backlit 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 (see Options), 5.28 Watts maximum (with standard features)
  • 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; programmable for flow proportional pulse (sampler/totalizer), flow and/or level alarm
  • Electrical Surge Protection: Sensor, 4-20mA outputs and AC power input
  • Operating Temp. (electronics): -5° to 140°F (-20° to 60°C)
  • Approximate Shipping Weight: 10 lbs. (4.5 kg)

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 150°F (-15 to 65°C)
  • Exposed Materials: PVC, 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


  • Data Logging: Programmable 2-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
  • 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 steel with connection terminal strip
  • Power Input: 9-32VDC (2.5 W min., 6.5 W max.)
  • Enclosure Heater: Thermostatically controlled - 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

  • Sewer Flow Monitoring and Reporting
  • Industrial Effluent
  • Stormwater Monitoring
  • Natural Streams
  • Irrigation Water

  • Measure flow in pipes and open channels of any shape
  • Ideal where flumes or weirs are difficult to install
  • Works with water level from 1' (25.4 mm) to 15 ft (4.5 m)
  • Auto-detects field installation of options including data logger and control relays

The AVFM 5.0 Area-Velocity Flow Meter includes a submerged ultrasonic sensor that is installed at the bottom of an open pipe or channel. Exposed materials are plastic so the sensor resists fouling and corrosion. It has no moving parts and no orifices, ports or electrodes.

The AVFM 5.0 displays and totalizes flow. It includes three 4-20mA outputs (Flow, Level and Velocity), plus two control relays for level alarms or flow proportionate pulse output for samplers and chlorinators. It is easy to calibrate with the built-in keypad and menu system. A built-in 2-million point data logger with USB output is optional. Intrinsic Safety Barriers for sensor and cable installation in hazardous rated channels is also optional.

SCOPE: This specification covers an ultrasonic, area-velocity flow monitor as manufactured by Greyline Instruments, Massena, New York / Long Sault, Ontario. The instrument shall provide for indicating, transmitting, totalizing of the flow rate through partially filled or surcharged round pipes and rectangular, trapezoidal, egg or irregular shaped open channels.


  1. Flow Monitor to consist of a submersible ultrasonic sensor, connecting cable, and remote enclosure with indicating, transmitting and controlling electronics. System shall have no moving parts.
  2. Level measurement accuracy shall be ±0.25% of Range. Velocity measurement accuracy shall be ±2% of reading.

Sensing Element

  1. Ultrasonic sensor shall be designed for continuous submersion in liquids.
  2. Using the Doppler principle, the sensor shall measure fluid velocities from 0.1 to 20 ft/sec (0.03 to 6.2 m/sec) and reverse flow to -5 ft/sec (-1.5 m/sec).
  3. Using ultrasonic echo-ranging principle, the submerged sensor shall measure liquid level from 1' to 15 ft. (25.4 mm to 4.57 m). Minimum level shall not be greater than 1' (25.4 mm). Level sensing circuitry shall include a temperature sensor for automatic temperature compensation.
  4. Sensor shall be constructed of PVC and epoxy resin.
  5. Sensor operating temperature shall be 5°F to 150°F (-15°C to 65°C).
  6. Shall include manufacturer's recommended stainless steel sensor mounting bracket.

Sensor Connecting Cable

  1. Provide minimum length 25 ft (7.6 m) tri-coaxial cable with potted bond to the Sensor head. Sensor cable shall be waterproof and electrically shielded. Exposed material shall be polyurethane only.
  2. Extended sensor cable shall be shielded tri-coaxial to a maximum length of 500 ft (152m). Cable shall be spliced with screw terminal connections in manufacturer’s recommended steel NEMA4 Junction Box.


  1. The transmitter shall provide for field calibration to round pipes and open channels of any shape.
  2. Calibration shall be via built-in 5-key calibration system with menu selection of parameters. Systems requiring calibration by Parameter codes, BCD switches or external calibrators shall not be accepted.
  3. Calibration data shall be password protected and permanently stored through power interruptions for a minimum of 12 months.
  4. Field calibration shall allow selection and automatic conversion of measurement units, measurement span, high/low flow alarm relay and flow proportional relay pulse rates.
  5. Transmitter shall permit field programmable damping to smooth output in turbulent flow conditions.
  6. Transmitter operating temperature shall be from -5° to 140°F (-20° to 60°C). Transmitter shall contain a thermostat-controlled enclosure heater for condensation protection below 30°F (-1°C).
  7. Transmitter shall have three isolated 4-20mA outputs rated for 1000 ohm maximum load with menu-selectable 0-5VDC alternative. Outputs shall be configured to transmit level, velocity and flow.
  8. Provide two relay contacts rated 5 amp SPDT programmable for flow proportionate pulse to a remote totalizer or sampler, high-low flow, velocity and/or level alarm, echo loss alarm.
  9. Provide a white, backlit matrix LCD display indicating flow rate, level, velocity, relay states and 16-digit totalizer in user-selected engineering units.
  10. Transmitter display indicating flow rate, units of calibration, totalizer and relay states shall be visible without opening cover.
  11. Transmitter shall be housed in a wall-mount, watertight NEMA4X (IP66) enclosure with hinged, clear cover. Mounting hardware shall be included.
  12. Transmitter electronics shall be surge protected on AC power input, sensor and 4-20mA outputs.
  13. Transmitter power input shall be 100-240VAC 50-60Hz with power consumption of 5.28 Watts or less.
  14. The transmitter shall permit plug-in field installation and auto-detection of optional accessories including data logger and additional control relays.

Optional Features For Insertion As Required


  1. Have separate, submerged Doppler velocity sensor, plus a non-contacting ultrasonic level sensor mounted above the liquid. Doppler velocity sensor shall be designed for continuous submersion in liquids and rated for fluid velocities from 0.1 to 20 ft/sec (0.03 to 6.2 m/sec) and reverse flow to -5 ft/sec (-1.5 m/sec). Non-contacting ultrasonic level sensor shall be rated for measurement range from 8' to 12 ft. (203.2 mm to 3.66 m) and shall include integral temperature compensation.
  2. Sensor cable shall be 50 ft. (15 m) continuous length with potted bond to the Sensor head.
  3. Sensor cable shall be 100 ft. (30 m) continuous length with potted bond to the Sensor head.
  4. Separate length extended sensor cable shall be shielded tri-coaxial to a total maximum length of 500 ft (152m). Cable shall be spliced with screw terminal connections in manufacturers recommended steel NEMA4 Junction Box.
  5. Sensor and connecting cable shall be rated intrinsically safe to Class I,II,III, Div. I,II, Groups C,D,E,F,G for installation in hazardous locations.
  6. Sensor shall mount with manufacturer's stainless steel mounting band for specified pipe diameter from 6' to 72' (150 to 1800 mm).


  1. Have a built-in Have a built-in 2 million point Data Logger with USB output to flash drives or mass storage devices. Data logger shall support time and date-stamped logging and generate formatted flow reports including total, average, minimum, maximum and times of occurrence. Include Windows software for data log graphing and export.
  2. Have a thermostat controlled enclosure heater for Transmitter operation at temperatures below freezing.
  3. Have manufacturer's recommended enclosure sunscreen to permit Electronics enclosure mounting in direct sunlight.
  4. Transmitter power input shall be 9-32VDC with minimum power consumption of 2.5 W to 6.5 W max.


Area-Velocity Flow Monitor shall be Greyline Model AVFM 5.0 and warranted against defects in materials and workmanship for one year.

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