Transit-time ultrasonic flow meter & doppler ultrasonic flow meter difference

 Transit-time ultrasonic flow meter & doppler ultrasonic flow meter difference

Transit-time ultrasonic flow meter and doppler ultrasonic flow meter all adopt clamp on sensor measurement, could be used in different working conditions, transit-time ultrasonic flow meter and doppler ultrasonic flow meter all their own advantages compare with each other.

We like the difference as below for easy recommendation.

1. The measurement principle is different. The main principle of the transit-time method is that when the ultrasonic beam propagates in the liquid, the flow of the liquid will cause a small change in the propagation time, and the change in the propagation time is proportional to the flow rate of the liquid. At zero flow, the two sensors take exactly the same amount of time to transmit and receive sound waves (the only technology that can actually measure zero flow). When the liquid is flowing, the acoustic wave transit time in the upstream direction is greater than that in the downstream direction. The Doppler method works by taking advantage of the fact that the ultrasonic wave will be scattered if it encounters tiny solid particles or bubbles in the propagation path.  

2. The applicable medium is different. The transit-time ultrasonic flowmeter can only measure relatively clean liquids, and it cannot work well when it encounters more solid particles or air bubbles. The Doppler method uses the characteristics of ultrasonic waves to be scattered, so the Doppler method is suitable for measuring fluids containing solid particles or bubbles, but clean liquids cannot be measured.

3. The measurement accuracy is different. The transit-time method has higher measurement accuracy, and the Doppler method has lower measurement accuracy. Due to the random existence of scattering particles or bubbles, the sound transmission performance of fluids is also different. If the fluid with poor sound transmission performance is measured, the scattering is stronger in the low flow velocity area near the pipe wall; while the fluid with good sound transmission performance is measured at high The scattering in the flow velocity region is dominant, which makes the measurement accuracy of the Doppler method low. Although the structure in which the transmitting transducer is separated from the receiving transducer is adopted, so that only the scattering in the middle area of ​​the flow velocity section can be received, the measurement accuracy is still lower compared with the time difference method.

4. The working conditions are different. The transit-time method is suitable for full pipe measurement, while the Doppler method is suitable for measuring the flow of full pipes, partial pipes, open channels, etc.




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