Acoustic interferometer

About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.

The measurement of mechanical and electrical parameters of liquids

Abstract: The sensor for the measurement of mechanical and electrical parameters of liquids such as viscosity, density, elasticity constant, permittivity, and electrical conductivity was developed. The sensor is based on the plate of YX lithium niobate with thickness 200 micron. There are two input and two output interdigital transducers (IDT) for launching and receiving SH0 wave and also container for liquid under study on the plate surface. The aluminum film is deposited on the lower side of plate between one pair of transducers. The continuous electromagnetic signal from HF generator is applied on the input IDTs. SH0 wave passes under the container and transforms into output electromagnetic signal, which follows in vector voltmeter. When the liquid under study is put into container the velocity and attenuation of wave changes that leads to the change in phase and amplitude of output electromagnetic signals. Acoustic wave passing through electrically open channel is reacted to mechanical and electrical parameters of liquid. The wave passing through electrically shorted channel is reacted only to mechanical liquid parameters. The measured values of changes in phase and amplitudes of output signals allow to determine the sought parameters of liquid by using the special calculation program. The developed sensor may be used as the liquid identifier in food and chemistry industries and for time monitoring of various biological reactions. At present time there exist a great number of papers devoted to problem of propagation of plane inhomogeneous acoustic waves in solid wave-guides of various types contacting with liquids of different kinds. The most general and detailed review of these papers is presented in monograph [1]. From all types of considered waves the most interesting ones are the acoustic waves with shearhorizontal polarization (SH surface acoustic waves (SAW) and SH plate acoustic waves). These waves can propagate in contact with liquid without significant radiation loss concerned with launching the acoustic energy into liquid [1]. It is explained by the fact that the component of mechanical displacement laying in the surface of plate and being normal to the wave vector prevails over other components. Nevertheless the presence of liquid may lead to significant change in velocity as well as in wave attenuation. It is well known that these changes may be caused by such liquid parameters as viscosity, elasticity and density [1] and also permittivity and electrical conductivity for piezoactive waves [1]. The aforementioned properties of SH waves allowed developing the various sensors based on SH SAW as well as on SH plate waves. These sensors are widely used for determination of the quality of food and everyday liquids [2,3], for determination of quantity of solid particles in liquids [4], for measuring the viscosity [1,5,6], conductivity [1,7,8], and for monitoring of biological reactions [1]. At that in known papers SH SAW and SH plate waves in thick compared to wavelength λ plates were only investigated. Bur recent studies of plate acoustic waves in thin in comparison with wavelength piezoelectric plates have shown that these waves have the more electromechanical coupling coefficient [9] and more gravimetric sensitivity [10] in comparison with mentioned above waves. This leads to stronger influence of liquid presence on wave parameters and to more their sensitivity to change in one or another liquid parameter [11]. This fact apparently may lead to increase of measurement accuracy of pointed liquid parameters. Fig.1 and 2 show the dependencies of velocity (a) and attenuation (b) SH0 acoustic waves in plate of Y-X lithium niobate plate on conductivity of contacted liquid and its viscosity, respectively. One can see that for normalized plate thickness h/λ = 0.1 the change in liquid conductivity from 10 -4 up to 100 (Ohm × m) -1 leads to the change in velocity 6% at the frequency 3 MHz. At that the attenuation changes from 0 up to 1.7 dB/λ. As for liquid viscosity its change from 0 to 10000 N×s/m 2 at the same frequency causes the increase in velocity ~5%. In this case the attenuation increases from 0.2 to 2 dB/λ.

Atmospheric variable compensation for an automated inspection system

Abstract: A phase-monitoring type of acoustic inspection system includes acoustic transducers (21) to transmit and receive continuous acoustic waves at a constant frequency, a detector (45) to detect changes in phase or amplitude, or both, of acoustic waves reflected at different times from a fixed reference target through an isothermal transmission medium, and a conditioning system (25) to control the temperature of the acoustic transmission path in response to the detected changes associated with the reference target to maintain the wavelength of acoustic waves constant regardless of changes in humidity and barometric pressure along acoustic transmission paths.

Temperature stable pseudo-surfase acoustic waves on lithium tantalate [pseudo-surfase read pseudo-surface]

Abstract: Full contour maps of basic propagation characteristics of pseudo-surface acoustic waves on LiTaO3 are calculated and plotted. Orientations, in which temperature stable pseudo-surface acoustic waves exist, were found. In particular this is a range of Euler angles I = 30 o ,T = 30 o - 40 o ,\ = 116 o - 125 o .

Acoustic channels and lenses in a medium with inhomogeneous velocity field

Abstract: A homogeneous moving medium can feature waveguide propagation of acoustic oscillations, provided that the velocity of medium is inhomogeneous. A waveguide of a finite length is equivalent to a lens. The waveguides and lenses are nonreciprocal, whereby their characteristics are significantly different for the acoustic waves propagating in opposite directions. Estimates are obtained and the possible applications are discussed.