A Novel Approach to Acoustic Liquid Density Measurements Using a Buffer Rod Based Measuring Cell

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 plusmn0.15% of the reference values. A comparison of the measured densities based on both a time-domain and a l2-norm frequency domain integration signal processing approach is given, along with a recommendation as to how the signal processing should be performed.