ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

5pEA2. Transit time determination in a one-way ultrasonic measurement system.

Magne Vestrheim

Steinar Vervik

Murugendran Kanagasundram

Dept. of Phys., Univ. of Bergen, Allegt. 55, N-5007 Bergen, Norway

Frequency and time domain analysis are used to study the transit time determination in a one-way ultrasonic measurement system for gases at around 200 kHz. Effects of transducers, diffraction, and interfacing to electronics on pulse forms and transit times are considered. Comparisons are made with experimental results using two transducers mounted in a stabilized acoustic chamber where fluctuations can be reduced so as not to affect amplitude and time measurement accuracies. By utilizing a fitted model for the transmitting responses of the transducers together with measured impedance data and the assumption of reciprocity, a useful modeling of the signal transmission through the system is achieved. The effects of receiving electronics and cabling are also measured and included. The results are used to discuss effects on the transit times for recent precision multibeam ultrasonic flowmeters used in the transport of natural gas, and at resolution and accuracies required in the zero calibration of such meters. [Work performed in cooperation with Christian Michelsen Research, Bergen.]