ABSTRACT
This paper presents the implementation of the relative reflection method for the ultrasonic measurement of the density of liquids, which may be flowing in pipelines, at different temperatures. This technique will be shown to be valid for large-diameter tubes containing flowing liquids. It employs a double-element transducer, consisting of a piezoelectric ceramic transmitter and a large aperture PVDF membrane receiver, separated by a polymethylmethacrylate buffer rod. Between the receiver and the liquid is a PMMA reference rod. The density is obtained from the reflection coefficient of the reference rod-liquid interface and the transit time between this interface and a reflector placed in the opposite wall of the tube. The DET is calibrated once to account for temperature effects. The calibration is incorporated during signal processing, so that the actual density measurement is temperature compensated. In testing this method, a system was implemented and measurements of several liquids, stationary and flowing in a pipeline, were conducted. The error of measurements obtained by this method for distilled water, tap water, castor oil, and ethanol, when compared to data in the literature or obtained by a pycnometer, is less than 1.5%
ABSTRACT
The relative transmissivities of several commonly used ultrasonic coupling agents were measured to determine if there were significant differences in their effectiveness. Coupling media were evaluated in thin films to simulate clinical use. In order to minimize experimental error in this determination, transmitted energy was measured in the far field of the sonating transducer; the receiving transducer was angled slightly to minimize standing waves; and the sonating chamber was made as anechoic as possible. It was found that there is no practical difference in the transmissivities of the common coupling agents, except that hydrocortisone ointments and creams had lower transmissivities, probably due to microscopically entrapped air. When used as a thin film, absorption of ultrasound in the media was insignificant, and variation in transducer pressure was found to cause differences in energy transmitted greater than those found between the common coupling media. Consequently, it was concluded that coupling media can be chosen primarily on the basis of cost and convenience.
