The working principle of a Ultrasonic flow meter is based on the transit-time Technology. The ultrasonic flow meter utilizes two ultrasonic transducers that function as both ultrasonic transmitter and receiver. The ultrasonic flow meter operates by alternately transmitting and receiving a burst of ultrasound between the two transducers by measuring the transit time that it takes for sound to travel between the two transducers in both directions. The difference in the transit time t measured is directly proportional to the velocity ( V) of the liquid in the pipe. With no flow, the transit time will be equal in both directions. With flow ultrasound will travel faster in direction of flow &slower against the flow. The liquid velocity (V) inside the pipe can be related to the difference in time of flight through the following equation:
V = K x Dx t
Where V: Velocity of the Liquid
K: Constant
D: Distance between the two transducers
t: Difference in transmit time