### Details

The Time Transit Difference Correlation Principles makes use of 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 meter work accorcding to this transit-time principle:

Vf = Kdt/TL

Where:

Kf: velocity

K: Constant

dt: Difference in time of flight

TL: Average 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 then 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.