Ultrasonic meters (USMs) have become widely used custody transfer meters for gas transmission and distribution measurement
systems. USMs have taken the place of measurement stations that have historically utilized orifice metering. While orifice
metering has been a good form of measurement, technology has driven the demand for a new, more effective form of fiscal
measurement. USMs are not only being installed in new measurement stations but are also being used to upgrade/retrofit
legacy orifice metering stations. For all custody transfer applications, users require flow calibrations to improve meter
performance and overall measurement uncertainty. The latest revision of AGA Report No. 9, Measurement of Gas by Multipath
Ultrasonic Meters, Fourth Addition [Ref 1], requires flow calibration for ultrasonic flow meters when being used for custody
transfer applications. Some users will also still choose to flow calibrate USMs that are installed in non-custody applications,
but where accurate measurement is still critical.