The SGM-100 utilizes two transducers which work as ultrasonic transmitters and receivers. They are clamped on the outside of a closed pipe at a specific distance from each other. They can be mounted in a V position (the sound crosses the pipe twice), in a W position (the sound crosses the pipe 4 times) or in a Z position (mounted on opposite sides of the pipe – the sound crosses the pipe once). The selection of the mounting position depends on the pipe and liquid characteristics.

The SGM-100 operates by alternately transmitting and receiving a frequency modulated burst of sound energy between the two transducers and measuring the transit time that takes the sound to travel between them. The difference in measured transit time is directly and exactly related to the velocity of the liquid inside the pipe.