The picture on the left shows the transmitting impulses and the resulting received signals. Through the difference in the received signals, the transit time difference can be determined.
Since the difference in transit time is very slight (picoseconds), the calculation is done with a multi-step correlation method.
With an increasing flow, the transit time difference of the received signals increases as well. By adjusting the sensor, it is possible to convert the transit time difference into a volumetric flow.