Types of Ultrasonic Flow Meters

Transit Time vs Doppler: What’s the Difference?

Ultrasonic flow meters come in two main types, each designed for specific fluid conditions and application needs.

Transit Time Meters are ideal for clean, single-phase fluids. These meters work by comparing the time it takes for ultrasonic signals to travel upstream and downstream through the fluid. A difference in travel time reveals the flow rate.

Doppler Meters, on the other hand, are better suited for dirty or aerated fluids. They detect frequency changes caused by particles or bubbles moving in the flow stream.

Choosing the Right Type of Ultrasonic Flow Meter

Your choice depends on the nature of your fluid and installation requirements:

  • Transit Time Meters:
    • Best for clean liquids like potable water, glycol, or oils
    • Higher accuracy under ideal conditions
    • Requires full pipes and low turbulence
  • Doppler Meters:
    • Ideal for wastewater, slurries, and suspensions
    • Handles aerated or particulate-rich flows
    • More forgiving in variable conditions

Clamp-On Flexibility

Both types are available in clamp-on designs, which mount externally without disrupting existing piping. This makes them perfect for retrofit projects or temporary flow audits.

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