米6体育平台手机版

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

Trademarks
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
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
3References
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 = \frac{L}{2} \times (\frac{1}{T_{12}} - \frac{1}{T_{21}}) = \frac{L}{2} \times \frac{T_{21} - T_{12}}{T_{21} T_{12}} = \frac{L}{2} \times \frac{ΔT}{T_{21} T_{12}}

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.