Ultrasonic interferometric sensor for rheological changes of fluids

An ultrasonic interferometric sensor has been introduced for the measurement of subtle changes in the physical properties of fluids such as density, viscosity, and bulk modulus. Tone burst ultrasonic waves are generated using a single peizocrystal bonded in between two solid delay line media of slightly different lengths. One side is in contact with a reference fluid (with known properties) and the other with a fluid whose properties are to be measured. The ultrasonic waves reflect from the two solid-fluid boundaries and are received back by the peizocrystal where the interference effects are measured. The longitudinal waves were used to measure the longitudinal impedance, while shear waves were used to measure the shear impedance. Glycerin-water mixtures were used as the test material. A simple plane wave model was shown to provide satisfactory comparison with experiments. Various parameters that influence the measurement were studied. © 2006 American Institute of Physics.