Patent ID: 6691577
Filing Date: 2004-02-17
Classification: A61B,B06B,G01F,G01N,G01P,G01S

Abstract:
An ultrasonic moving-speed measuring system comprising:a piezoelectric substrate; a first electrode formed on an upper end surface of said piezoelectric substrate; a second electrode formed on a lower end surface of said piezoelectric substrate and located at the corresponding position with said first electrode; an interdigital transducer formed on said upper end surface of said piezoelectric substrate; and a signal analyzer, said first- and second electrodes forming a thickness-vibration mode transducer, said piezoelectric substrate, said thickness-vibration mode transducer, and said interdigital transducer forming a transducing assembly, said thickness-vibration mode transducer receiving an input electric signal with a carrier frequency approximately equal to the center frequency for operating said thickness-vibration mode transducer, and radiating a longitudinal wave into a medium that is in touch with the bottom of said transducing assembly, and then, making a material in said medium reflect said longitudinal wave back, said interdigital transducer detecting a delayed electric signal with a Doppler frequency via a mode conversion from a reflected longitudinal wave to a leaky Lamb wave, said signal analyzer sensing a moving speed of said material from a difference between said carrier- and Doppler frequencies.