How does the ultrasonics measure the flow?

The SONIC-PRO® MS6/S6A meter uses the ultrasonic transit Transit-Time method to measure fluid flow in virtually any fluid in which sound waves can travel. The transducers, which generate and receive the sound waves, are located inside the fluid path and contain no moving parts. This method is extremely sensitive and can detect very low and high flow rates with no pressure losses due to the measuring principle.

The time-measuring method requires relatively “clean” fluid to enable the sound waves to complete their circuit. Therefore, large amounts of particles or large bubbles and air gaps may interfere with the sound waves and reduce or eliminate the ability of the meter to calculate flow.

The Transit Time measurement method works by sending a short ultrasonic signal burst first in one direction and then in the other between two transducers separated along the length of the meter. When traveling in the same direction as fluid flow, the burst is carried along by the fluid and arrives earlier as a result. When traveling against fluid flow, the burst is held back by the fluid and arrives later. The MS6/S6A measures this difference in time-of-flight in the two directions and calculates the fluid flow rate.