SLAA889A March   2019  – July 2021 MSP430FR6041 , MSP430FR6043 , MSP430FR60431 , MSP430FR6045 , MSP430FR6047 , MSP430FR60471

 

  1.   Trademarks
  2. 1Flow Metering Background
    1. 1.1 Water Flow Velocity Estimation
      1. 1.1.1 Velocity of Ultrasound in Water is Known
      2. 1.1.2 Velocity of Ultrasound in Water is Unknown
  3. 2Algorithms for Ultrasonic Water Flow Metering
    1. 2.1 Correlation Based Technique for Differential TOF Estimation
    2. 2.2 Absolute Time-of-Flight (AbsTOF) Measurement (Tup and Tdn)
      1. 2.2.1 AbsTOF Calculation
        1. 2.2.1.1 Acquisition Algorithm for AbsTOF
        2. 2.2.1.2 Tracking Algorithm for AbsTOF
  4. 3References
  5. 4Revision History

1.1.2 Velocity of Ultrasound in Water is Unknown

If the velocity of ultrasound in water is unknown, Equation 6 can be used to solve for the velocity of the water flow.

Equation 6. v=L2×1T12–1T21=L2×T21–T12T21T12=L2×ΔTT21T12

This equation needs the propagation times [or absolute times of flight (AbsTOF)] T12 and T21 in the two directions along the cross section of the pipe. The TI solution implements this technique so that the velocity of sound in water is not required for accurate measurement of water flow velocity.