Improved ultrasonic interferometer technique for propagation velocity and attenuation measurement in liquids

Abstract

Propagation velocity and attenuation are the two basic parameters used for the ultrasonic investigations of liquids. An ultrasonic interferometer is a widely used tool as a cost effective solution for propagation velocity measurement. The ultrasonic attenuation measurements are not possible using the existing interferometers commercially available in the market. Ultrasonic attenuation can be measured using the pulse echo method, which is relatively complex and expensive. Generally, in interferometers, a radio frequency voltage of more than 100 V is used to excite the piezoelectric transducer. In this article, an improved design of the ultrasonic interferometer with low (5 V) rf voltage excitation is discussed. The proposed design has several advantages over existing systems. The low voltage excitation reduces heating of the sample under study. Detection of the received signal is done directly at the transducer. The critical effects of a coaxial cable in rf detection are minimized by dc detection at the transducer node. The impedance response of the transducer is used for the detection of nodes and antinodes for attenuation and velocity measurements. The use of an instrumentation amplifier enables one to amplify the extremely small voltage changes across the transducer due to interference. The developed method has the capability to measure attenuation due to high receiver sensitivity. The technique has been validated for the propagation velocity and attenuation measurement in standard samples of water and other liquids. The results thus obtained have been compared with the literature and the conventional pulse echo technique which shows close agreement.

Accuracy Estimation of Propagation Velocity in Variable Path Ultrasonic Interferometer for Liquids

“…( 3), it may be inferred that fixedpath variable frequency interferometer system may prove to be relatively more accurate over the variable distance as the distance kept constant and frequency may be controlled more precisely and accurately. With advent of direct digital synthesis (DDS) technology-based signal generator, it is possible to have flexibility to adjust the frequency with 1 Hz step with an accuracy of about 50 ppm levels [20].…”

“…In the other interferometric method, the path of ultrasound is kept constant and the frequency of the radio frequency (RF) source is changed so that maxima and minima are detected [19]. With the advent of direct digital synthesis (DDS) technology, it is possible to vary the ultrasound source frequency at small steps (Hz) to precisely change the wavelength in the sample [20]. The variation in the radio frequency is generally preferred within the 3 dB bandwidth of the ultrasonic transducers.…”

Milk as a Complex Multiphase Polydisperse System: Approaches for the Quantitative and Qualitative Analysis

“…When the distance between transducer and reflector changes, the intensity oscillations are measured, corresponding to the maxima and minima of the ultrasonic wave along its propagation path with a step of the half wavelength. Description of devices, principles of use, and improvements of the ultrasonic interferometer technique can be found in [138][139][140]. Furthermore, some devices of the ultrasonic interferometer include optical diffraction, which allows expanding its analytical capabilities [141].…”