AV-Flow Transmitter

Code: QT001

Specify language: English, French, Spanish, Italian, Portuguese

High performance flow transmitter designed for use as a system component in open channel and part-filled pipe applications.

This product operates with:

  • Level Sensor standard 10 metre length (varying lengths available upon application)
  • Velocity Sensor standard 10 metre length (varying lengths available upon application)
  • Comms Cable (USB or RS232)
  • Software
  • User Manual


AV-FLOW TRANSMITTER with Velocity and Level Sensor
AV-FLOW TRANSMITTER with Velocity and Level Sensor AV-FLOW TRANSMITTER with Velocity and Level Sensor Enlarge
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system details

download datasheet

  • Benefits & Features
  • Measurement Principles
  • Product Features
  • Product Hardware
  • Powerful, easy to use PC software simplifies transmitter commissioning
  • Quick to install – no weirs or flumes
  • Velocity measurement from 10mm/S up to 5m/S
  • High sensitivity extends applications to ‘clean’ water
  • Streamlined velocity probe eliminates fouling and reduces flow disturbances
  • Real-time processing of velocity signals thereby reducing power consumption
  • Smart power saving mode – intelligent use of power saving which automatically reduces the measurement time for high flow velocities and high signal qualities and increases the measurement time for low velocities and low signal qualities
  • External Power monitoring via the UI
  • Sophisticated ultrasound processing ignores spurious signals
  • Ultrasound signal quality monitor confirms measurement integrity
  • Specified (constant) silt level taken into account in area calculation
  • Velocity correction factor calibration
  • Automatic recording of velocity signals and histograms for use in performance monitoring
  • Distances up to 500 m from system unit to velocity and level sensor. 300 m for ATEX velocity and level sensor

Mainstream uses the area-velocity method to give a continuous or time sample measurement of fluid flow.  Mainstream uses a streamlined probe that operates immersed in the flowing liquid. The velocity probe transmits utrasound into the liquid to create a zone of inspection. Bubbles and solid particles carried through this zone by the flow, even when present in only minute quantities, reflect ultrasound back to the probe. Only high quality signals containing verified velocity information is used, thereby ensuring measurement integrity.

This measured frequency shift in the ultrasound signals gives flow velocity.  The verified velocity signals produce a histogram of the flow velocities.  Analysing this histogram gives the mean flow velocity.

Liquid level is measured by a submerged  pressure transmitter or ultrasonic sensor.  The flow cross-sectional area is deduced from the liquid level measurement and the stored description of  the channel or pipe cross section.  The flow rate is the flow velocity multiplied by the flow cross-sectional area.


Transducer Type: Any 4:20 mA current loop level sensor
Method : Pulse activation with configurable sensor warm-up time. Loop current measurement by self-calibrating 16-bit delta-sigma A-D converter
Current Range : 0-30 mA
Resolution : Better than 1 µA
Transducer Calibration : Calibration table (maximum 23 points) with built-in interpolator converts loop current into level measurement. Simple transducer calibration tool included in UI software
Interchangability : Transducers and calibration data directly interchangeable between Mainstream system units


Transducer Type: Submerged ultrasonic sensor containing signal generator, transmitter, receiver and decoder electronics
Method : Phase Coherence time delay measurement determines the time for tracers carried by the flow to travel a fixed distance (~ 0.75 mm)
Velocity Range : -5 m/s to -10 mm/s and 10 mm/s to 5 m/s
Resolution : Better than 1 mm/s
Measurement Integrity : Ultrasound signal quality monitor gives the percentage of the measurement time that the received ultrasound signal contains useful velocity information
Smart Power Saving : Each velocity measurement is based on the same quantity of information. Automatically reduces the measurement time for high flow velocities and high signal qualities and increases the measurement time for low velocities and low signal qualities


Area : Flow cross-sectional area calculated from the level measurement and the dimensions of the pipe or channel. Calculation can take into account a specified (constant) silt level. Flow cross-section specification tools included in UI software
Flow Rate : Fluid flow rate calculated by multiplying cross-sectional area by flow velocity
Flow Quantity Three independent flow totalisers calculate forward only, reverse only, and forward-reverse flow quantities. Each totaliser uses separate elements to accumulate hour quantity and total quantity to prevent round-off errors


Power Inputs : Connectors for external 12V and 24V supplies
External 12V supply : Connection for external 12V
External 24V supply : Connection for external 24V
Power Supply Monitor : Power monitoring circuits track supply status. Supply voltages can be viewed via the UI


Local : RS232 and USB compatible interface with automatic baud rate detection. Supports 1200, 2400, 4800, 9600, 14400, 19200, 38400, 57600 and 115200 baud
Remote : Optional external SDI or GPRS device
Software : Mainstream Communicator UI software for system configuration, diagnostics, real- time measurement display and data retrieval. Mainstream Communicator runs on PC platforms under Windows 2000, XP, Vista, 7, 8, 8.1 and 10 with data transmission from device to PC, for data control, processing and export


Linear (pipe and channel dimensions): Selectable from mm, cm, m, in, ft
Level : Selectable from mm, cm, m, in, ft
Area : Selectable from m2, cm2, mm2, in2, ft2
Velocity : Selectable from mm/s, cm/s, m/s, in/s, ft/s, ft/min
Flow Rate : Selectable from l/s, m3/s, ft3/s, igal/s, USG/s, l/min, m3/min, ft3/min, igal/min, USG/min, m3/h, ft3/h, m3/d, Ml/d.
Display Format : Independently configurable display format for each measurement. Options are integer, fixed point with 1 to 6 decimal places, and scientific (E-format). Display defaults to scientific format if data cannot be correctly represented in selected format
4:20mA Outputs: One 4:20mA output. Configurable to selected measurands.


Materials : Titanium, acetal and polyurethane
Dimensions : 185 mm long x 17.5 mm diameter
Cable : 8 mm diameter vented polyurethane cable with Kelvar strain cord
Weight : 1 kg including standard 10 m cable length
Level Range : 0 to 2 m working. Maximum 8m overrange
Resolution : Better than 1mm
Combined Accuracy : Combined effects of non-linearity, hysterisis and repeatability better than 0.25% best straight line. Non-linearity and offsets removed by transducer calibration
Environmental Protection : Fully encapsulated to IP68
Operating Temperature : -20°C to 60°C (temperature compensated 2°C to 30°C)


Materials : Streamlined µPVC moulding and polyurethane cable
Dimensions : 105 mm long x 50 mm wide x 20 mm high
Cable : 8 mm diameter polyurethane cable with Aramid strain cord. Breaking load 45 kg. Minimum static bend radius 52 mm
Weight : 1 kg including standard 10 m cable length
Maximum Cable Length : 500 m
Environmental Protection : Totally encapsulated to IP 68
Operating Temperature : -10°C to 80°C
Minimum Operating Depth : 30 mm


Materials : Ultra pure cast aluminum
Dimensions : 220 mm wide x 120 mm deep x 80 mm high
Weight : 1.65 kg
Environmental Protection : Enclosure is IP67. Electronic assembly is encapsulated to IP68
Operating Temperature : -10°C to 70°C

product support

Please call: +44 (0) 1943 830111 or email: