• Designed for channels 6 ft (2 m) width or larger, and channels with irregular velocity profiles
  • Measures velocity + level to monitor flow with multiple ultrasonic sensors
  • Measures Forward and Reverse Flow
  • Velocity measurement range: 0.1 to 20 ft/sec and reverse flow to -5 ft/sec
  • Works with water level from 1" to 15 feet
  • Accuracy:
    • Level: ±0.25% of Range
    • Velocity: ±2% of Reading
    • Repeatability and Linearity: ±0.1%
  • 3 Isolated 4-20mA Outputs (Flow, Level and Velocity)
  • Totalizer and 2 Control Relays
  • Simple 5-key Calibration
  • Optional built-in 2-million point data logger and software with USB output to flash drives
  • Watertight and dust tight NEMA4X (IP 66) polycarbonate enclosure with shatterproof covers

What's in the Box

  • 3- submersible QZ02L ultrasonic velocity and level sensors
  • 3- 25 ft. shielded 3-coaxial sensor cable (optional lengths available)
  • AVQZ3 remote transmitter-receiver module
  • 3- Stainless steel sensor mounting brackets
  • Installation and operation manual


The Greyline Instruments AVMS 5.1 ultrasonic flow meter is designed to monitor flow through large open channels, partially full sewer pipes and surcharged pipes without a flume or weir making it ideal for municipal stormwater, stream flow, irrigation water, raw sewage, sluiceways, water intake channels, cooling water discharges and industrial effluent applications.

The AVMS 5.1 uses three submerged ultrasonic sensors to continuously measure both velocity and level in the channel. It is especially well-suited for channels wider than 6 feet or applications where velocity will vary across the width of the channel. By positioning three velocity sensors across the channel, variations in flow velocity can be accounted for and an average velocity profile determined. The AVMS 5.1 will automatically factor out zero readings at low flow rates if one or more sensors are not submerged or become covered in sediment.

The AVMS 5.1 can measure forward velocity up to 20 ft/sec (6 m/sec) and up to 5 ft/sec (1.5 m/sec) reverse velocity. The electronics and software sample and average flow rates continuously to provide stable readings. The flow rate and total flow can be viewed on the large backlit LCD display and three 4-20mA outputs and two control relays allow users to connect to external devices. Choose the built-in data logger option if you want the AVMS 5.1 to store time and date stamped flow values at 10 second to 60 minute intervals. Daily flow reports are automatically created. Windows software is included to display log files in graph and table formats, change measurement units and generate flow reports.

Setting up and using the AVMS 5.1 is simple. Careful selection of mounting location results in best performance and maintenance-free operation. Avoid locations where sediment builds up. The channel should not have drops or direction changes immediately upstream of the sensor and it should have a consistent cross section for one channel width upstream. Pipe or channel slope should not exceed 3%. No special compounds, tools or hardware are required. The sensors are completely sealed with no orifices or ports.