This document specifies requirements and recommendations for non-intrusive (clamp-on) ultrasonic flowmeters (USMs), which use the transit time of ultrasonic signals to measure the volumetric flowrate in closed conduits. Transit time flowmeters are predominantly used on single-phase fluids (liquid and gases) but can also be used where small quantities of additional phases are present.

This document specifies performance, calibration, and output characteristics, and deals with installation conditions.