Pressure or distance measurement using ultrasonics - involves compressible medium in which propagation velocity dependence on density is known

摘要

The method determines a pressure or a distance in a compressible medium whose external dimension or density, respectively, are known. The relationship between the velocity of propagation of ultrasonic waves in the medium and its compressibility and density are assumed to be known. An ultrasonic signal is transmitted through the medium and measurements are made of propagation time, thus enabling propagation velocity to be calculated. The ultrasonic frequency is of the order of 100 kH2. A reference measurement may be made using a signal at 10 MH2; at this frequency the pressure in the medium has negligible effect.