Abstract: A Karman vortex flow meter for measuring the flow rate of a fluid under test in a pipeline having a base to be secured to the pipeline, and a vortex detector having an axis intended to intersect the pipeline. The vortex detector includes a post, a detector flange at least partially surrounding the post having a free surface, a columnar force receiving part extending from the post into the pipeline for producing a Karman vortex, and a strain detecting element coupled to the free surface for detecting the Karman vortex and producing an output signal corresponding the detected Karman vortex.

Abstract: A Karman vortex flow meter for measuring the flow rate of a fluid under test in a pipeline having a base to be secured to the pipeline, and a vortex detector having an axis intended to intersect the pipeline. The vortex detector includes a post, a detector flange at least partially surrounding the post having a free surface, a columnar force receiving part extending from the post into the pipeline for producing a Karman vortex, and a strain detecting element coupled to the free surface for detecting the Karman vortex and producing an output signal corresponding to the detected Karman vortex.

Abstract: The apparatus of the present invention detects the resonant frequency of a vibratory member in contact with a fluid. The detection of the resonant frequency enables the device to be used to detect the density of a fluid which it is in contact with and thereby calculate the flow rate of the fluid. The vibratory member is mounted in a housing in such a way that the chambers on either side of the vibratory member have equal volumes. The fluid enters the device through a conduit and then divides into two equal tubes on either side of an extension of a vibratory member extending down these tubes. The apparatus for measuring the resonant frequency of the vibratory member is mounted on the vibratory member and is comprised of a piezoelectric element coupled to a driver circuit in a feedback loop.

Abstract: The apparatus of the present invention detects the resonant frequency of a vibratory member in contact with the fluid in order to determine the density or pressure of the fluid. The vibratory member is disposed in a housing to form a cavity with no flow communication between the side of the vibratory member facing into the cavity and the other side of the vibratory member. The vibratory member is vibrated by an annular piezoelectric device which may be attached to one or both sides of the vibratory member. An amplifier and feedback circuit regulate the frequency of oscillation of the piezoelectric device to that of the resonant frequency. The piezoelectric device may be comprised of several separate sections or several sections with partial interruptions in the piezoelectric material. Instead of the vibratory member and the piezoelectric transducer combination, the vibratory member may be constructed from a single fixed piezoelectric device with another piezoelectric disc mounted thereon.