Transit-time working principle
Principle of Measurement:
The Transit-time Correlation Principle makes use of the fact that the time-of-flight of an ultrasonic signal is affected by the flow velocity of the carrier medium. Like a swimmer working his way across a flowing river, an ultrasonic signal travels slower upstream than downstream.
Our TF1100 ultrasonic flow meters work according to this transit-lime principle:
Vf = Kdt/TL
dt: Difference in time of flight
TL: Ave rage Transit Time
When the flow meter works, the two transducers transmits and receives ultrasonic signals amplified by multi beam which travels firstly downstream and then upstream. Because ultra sound travels faster downstream than upstream, there will be a difference of time of flight (dt). When the flow is still, the time difference (dt) is zero. Therefore, as long as we know the time of flight both downstream and upstream, we can work out the time difference, and then the flow velocity (Vf) via the following formula.