Type of Ultrasonic meter are
1.Ultrasonic transit time
3.Ultrasonic open channel.
How ultrasonic transit time flow meter works?
Transit time flow meter utilize two transducers which function as both ultrasonic transmitter and receiver.They operate by alternatively transmitting and receiving a frequency modulated burst of sound energy between the two transducers.
The burst is first transmitted in the direction of fluid flow and then against fluid flow.Since sound energy in a moving liquid is carried faster when travels in the direction of fluid flow (downstream) than it does when it travels against fluid flow (upstream),a differential in the times of flight will occur.
The sound’s time of flight is accurately measured in both directions and the difference in time of flight calculated.
The doppler meter continuously transmits high frequency sound that travels the pipe wall and into the flowing liquid.
Sound is reflected back to the sensor from solids or bubbles in the fluid.If the fluid is in motion the echoes return at an altered frequency proportionate to flow velocity.
Doppler flow meter continuously measure this frequency shift to calculate the flow.
Open Channel Theory
Using ultrasonic level technology open channel flow meter include a non-contacting sensor mounted above the flume or weir.By measuring the time from transmission of an ultrasonic pulse to receipt of an echo ,the water level or head is accurately measured.