A novel approach to acoustic liquid density measurements using a buffer rod based measuring cell

Abstract

Abstract-A new method for measuring the pressure reflection coefficient in a buffer rod configuration is presented, together with experimental results for acoustic measurements of the liquid density, based on the measurement of the liquid's acoustic impedance. The method consists of using 2 buffers enclosing the liquid in a symmetrical arrangement with a transducer fixed to each buffer. One of the transducers is used in a pulse-echo mode while the other transducer operates as a receiver. The echo amplitudes leading to the pressure reflection coefficient as found by this method possess advantages such as reduced attenuation due to a shorter liquid transmission path and reduced interference, as compared with the ABC method. Measurements with distilled water and with special density calibration oil qualities have been performed using both the new method and the ABC method and are shown for the new method to give a density span within 0.15% of the reference values. A comparison of the measured densities based on both a time-domain and a l 2 -norm frequency domain integration signal processing approach is given, along with a recommendation as to how the signal processing should be performed.

Acoustic methods for obtaining the pressure reflection coefficient from a buffer rod based measurement cell

“…Therefore, a plane-wave approach with diffraction correction is taken. These aspects, along with an experimental realization using this measuring principle, are further described in [30].…”

“…A particular component of the systematic noise is the interference effect from the conversion of shear wave to compressional wave at the buffer-sample interface [32]. Using echo signals that do not interfere with such systematic noise components will be beneficial as the measurement of the echo signal's amplitudes leading to the reflection coefficient otherwise will be in error [30]. Also scattering both from within the buffers and the liquid is ignored.…”

“…Some of these new methods seem particularly suited for the measurement of high attenuation liquids, and they benefit from being able to obtain a reduced sensitivity of interference effects arising from mode conversion at the buffer-liquid interface, because these methods use a reduced time trace, compared with the ABC method. Experimental verification of some of these new methods in comparison with the ABC method will be given in an accompanying paper regarding acoustic measurement of liquid density [30], with more extensive results given in [35].…”

Structures and dynamics of microparticles in suspension studied using ultrasound scattering techniques

“…In cases where the equilibrium density cannot be employed, such as polymerization or structural formation processes, the simultaneous measurement could provide useful insight. The MERUS technique is different from previous literature but is similar to an ultrasound densitometer using a buffer rod . However, MERUS utilizes a disposable plastic cell (free from contamination attached to the buffer rod), and the error could be minimized by employing a reference to correct the small phase shift during measurements.…”

Ultrasonic rheology of visco-elastic materials using shear and longitudinal waves

“…Later, several authors have used the same kind of technique to determine the mass density of liquids. [4][5][6] Recently, a line-slab-line system was implemented to accurately determine the acoustic attenuation in a liquid layer from the analysis of the reflection of L pulses. 7 This technique has been used later to monitor the polymerization of an epoxy layer from the determination of L velocity and attenuation in epoxy.…”