Non-Contacting Doppler Flow Meters

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The Doppler Clamp-on and Open Channel Flow
Metering Technique
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Introduction

• Principle of operation.
• Modes of operation.
• Installation guidelines.

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The general principle of Doppler flow
measurement.
 
Approximate relationship between fluid velocity
and measured time. Does not include clamp on
transducer delays.
v is the speed of waves in the medium
vs is the velocity of the source
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Doppler Flow Measurement

• Continuous frequency is transmitted

How it Works

• Sound bounces off gas bubbles or particles in the
  fluid

• Reflected sound returns at an altered frequency

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Doppler Flow Technology

• Doppler Transmit

• Doppler Receive

• Doppler Shift

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Modes of operation

• - Single head
• Transmit and Receive Crystals in same Head

• - Dual-Head
• Transmit and Receive Crystals in separate Heads

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Installation guidelines

• Transducer positioning.
• Flow profiles

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Doppler Sensor Coupling
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Doppler Sensor Mounting
Doppler Sensor Mounting
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Doppler Sensor MountingAvoid Turbulent Flow

• Locate the Doppler Sensor 6 to 10 pipe diameters
  from Pipe Elbows or Tees
• Avoid highly Turbulent Flow locations

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Doppler Sensor MountingAvoid Laminar Flow

• Viscous or solids-bearing liquids develop a
  laminar profile
• Take readings at several locations and mount
  Sensor where flow is evenly distributed

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Doppler Sensor MountingAvoid Velocity-Increasing
Devices
PUMP
25 - 40 Pipe Diameters

• Locate the Doppler Sensor 25 to 40 Pipe Diameters
  from Pumps, Controlling Valves, Orifice Plates,
  Pipe Discharges or any other Velocity-Increasing
  Devices

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Doppler Sensor MountingAvoid Flow in Branch Lines

• Doppler ultrasonic signals can travel long
  distances in clean, non-aerated liquids
• Mount the Doppler Sensor 25 to 50 diameters from
  branch lines with flow

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Summary

• Principle of operation.
• Modes of operation.
• Installation guidelines.