Abstract

An ultrasonic flow sensor probe for measuring fluid (liquid or gas) flow (e.g., blood flow) in vessels or tubes provides decreased sensitivity to flow distribution non-uniformities and decreased overall size by employing multiple angled reflector surfaces which cause incident ultrasonic waves from one or more ultrasonic transducers to pass through the flow volume multiple times and in multiple directions without changing the planar orientation of the ultrasound waves. The wave paths resulting from the multiple reflections and multidirectional illumination of the flow volume decreases the probe's size and sensitivity to spatial distribution non-uniformities. The multiple angled reflector surfaces also permit the transmitting and receiving ultrasonic transducers to be placed close to one another, thereby reducing the overall probe size and making them particularly useful in flow measurements on small blood vessels in very small animals. In its simplest form, the present invention includes a two transducer probe with a first reflector surface positioned in the ultrasonic wave path of the first transducer, and a second reflector surface positioned in the wave path of the second transducer. The first reflector surface is positioned to reflect the ultrasonic wave from the first transducer toward the second reflector surface in a direction generally parallel to the flow direction of the vessel or tube. The second reflector surface then reflects the ultrasonic wave through the flow across the wave path from the first transducer and to the second transducer.