Patent ID: 6390999
Filing Date: 2002-05-21
Classification: A61M,G01F

Abstract:
A flow measuring apparatus comprising:an assembly for transmitting, in first and second directions, ultrasonic signals through fluid in a conduit and for receiving the transmitted ultrasonic signals transmitted in each of the first and second directions; circuitry operably coupled to the transmitting and receiving assembly for detecting phase shifts in the received ultrasonic signals relative to the ultrasonic signals transmitted in each of the first and second directions, the phase shift detecting circuitry configured to have a plurality of detection ranges each spanning substantially less than 360Â° and falling between 0Â° and 360Â° including an accuracy range wherein a physical response of said phase shift detecting circuitry to a phase shift occurring in said accuracy range is more accurate relative to a physical response of said phase shift detecting circuitry to a phase shift occurring in another of said plurality of detection ranges; and circuitry operably coupled to the phase shift detecting circuitry and configured for adjusting phase shifts in the received ultrasonic signals for detection by the phase shift detection circuitry in response to already-detected phase shifts in the received ultrasonic signals to enhance accurate detection of phase shifts by maintaining phase shifts detected by the phase shift detecting circuitry within said accuracy range of the phase shift detecting circuitry.