Flow instruments are vital tools used for verifying system and component performance. Traditionally, measuring flow is primarily accomplished using ultrasonic flow meters and magnetic flow meters (mag meters), which require significant installation labor and a considerable length of straight pipe to yield accurate results. Given the right conditions, ultrasonic and mag meters are effective; however, in other instances they can lead to decreased testing reliability. In applications where accurate flow measurements are needed and where system out-of-service time is a concern, SONARtrac flow meters are a viable solution to consider. This paper provides the theory of operation and technical justification behind the SONARtrac flow meter along with current industry applications.