Fuji Electric Co., Ltd.

Michihiko Tsuruoka

Noriomi Miyoshi

Wataru Nakagawa

Mutsumi Nagumo

Naohiro Kounosu

Osamu Kashimura

Masato Takahashi

Masashi Machida

Satoru Sakaue

Takahiro Kudo

Hiroyuki Yoshimura

Hironobu Yao

Kimihiro Nakamura

Etsuro Ito

Shuji Tsukamoto

Nobuhisa Kato

Yasuo Watabe

Iwao Matsumoto

Tadao Hashimoto

Keita Okawa

Masakazu Kawakami

Naohiro Konosu

Wataru Nakagama

Hiromi Suzawa

A capacitance-based pressure detecting apparatus detects a pressure applied to a diaphragm based on a capacitance which varies depending on the change in portion of the diaphragm. The pressure detecting apparatus comprises a diaphragm which changes position depending on a differential pressure between a first pressure and a second pressure, a first electrode which is provided opposite a first plane of the diaphragm and forms, together with the diaphragm, a first capacitor, a second electrode which is provided opposite a second plane of the diaphragm and forms, together with the diaphragm, a second capacitor, a third capacitor altering a capacitance according to the first pressure, a detecting unit for detecting the capacitance of the first through third capacitors, and an operation unit for obtaining a pressure applied to the diaphragm based on the capacitance of the first and second capacitors, and amending the obtained pressure based on the capacitance of the third capacitor.

Pressure detecting apparatus for measuring pressure based on detected

The invention concerns a Karman's vortex flow meter including dampening members for absorbing vibrations. A stopper is provided to permit limited movement between an amplifier casing and a supporting stand containing a flow detector. The stopper is coupled to one of the supporting stand and the casing and extends into a hole in the other of the supporting stand and the casing. The flow meter includes an elastic member positioned in the hole between the stopper and the other of the supporting stand and the casing so that the stopper and the other of the supporting stand and the casing are out of direct contact. The elastic member absorbs vibrations and prevents direct contact of the components to ensure accurate flow measurement.

Flow meter having a vibration dampener

A pneumatic infrared gas detector includes a pair of expansion chambers and a pair of pressure chambers, each of which is connected at one end thereof to the corresponding expansion chamber. Each of the pressure chambers is divided by a diaphragm into a first chamber connected to a corresponding expansion chamber, and a second chamber, such that the first chamber of one of the pair of pressure chambers is connected to the second chamber of the other of the pressure chambers through a first communication path, and such that the second chamber of the above-indicated one of the pressure chambers is connected to the first chamber of the other of the pressure chambers through a second communication path. A pair of pneumatic pressure detecting elements are provided each of which includes an electret film having one surface on which an electrode is formed, and an electrode plate disposed in opposed relationship with the electret film. The electret film is formed on a first side of a corresponding one of the diaphragms in each pressure chamber, and the electrode plate is supported and fixed at a position that is opposed to a second side of the corresponding diaphragm.

Pneumatic infrared gas detector

The precision of phase difference obtained by a phase difference calculating unit is improved by correction through outputs of a frequency ratio calculating unit and a temperature calculating unit considering that the phase or time difference of each output signal of a vibration sensor indicating the mass flow or density of a fluid is a function of the temperature and axial force on a measurement pipe, or that the axial force is a function of the ratio between two resonant frequencies.

Vibration measuring instrument

A second torsional vibrator having an outer frame and a second torsional spring is formed on the outer side of a first torsional vibrator having a pair of torsional springs and a plate member (reflection mirror), with a second torsional vibrator being fixed by the fixed part. The resonant frequency for the first torsional vibrator is set higher than that for the second torsional vibrator. The outer frame in the second torsional vibrator is driven substantially at the resonant frequency of the first torsional vibrator by an electromagnetic or electrostatic force. As a result, it becomes possible to obtain a stable and large scanning angle by using only a small driving force.

Torsional vibrators and light deflectors using the torsional vibrator

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.

Karman vortex flow meter

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.

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.

Vibration type transducer

In a Karman vortex flow meter, the variation of pressure caused near both sides of a Karman vortex forming unit inserted into the stream of fluid is applied to an oscillating member which is oscillating in a self-excited mode at a resonance frequency, so that the vortex frequency; i.e., the volume flow rate is detected from the modulation of the resonance frequency which is caused by variation of pressure or density attributing to the vortexes formed.

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. In this configuration one of the devices is used to mechanically excite the other and through a feedback circuit establish the resonant frequency of the two laminated piezoelectric devices.

A vibrating transducer for detecting the resonant frequency of a vibrating diaphragm and using that frequency to determine the pressure or density of a fluid contacting the diaphragm. The device includes a container having a diaphragm separating the cavity in the container into two chambers with the diaphragm preventing flow communication between the two chambers. A first fluid inlet in flow communication with the first chamber introduces fluid to the first chamber with that first chamber having an acoustic compliance less than the mechanical compliance of the diaphragm. The second fluid input is in flow communication with the second chamber and introduces fluid into the second chamber. By controlling the acoustic compliance of the chamber with respect to the diaphragm accurate measurements of the density or pressure of the fluid can be obtained.

Vibrating type transducer

A Karman vortex flow meter including an upstream columnar body having a substantially isosceles triangular cross section and a downstream columnar body having a substantially isosceles trapezoidal cross section. The downstream columnar body has a base surface which is substantially equal in width to the base surface of the upstream columnar body. The two bodies are positioned in a stream of a fluid with their base surfaces disposed at a distance from each other in mutually parallel relation and at right angles to the stream for generating Karman vortices to measure the flowing speed or rate of the fluid based on the frequency of the vortices. The upstream columnar body has a pair of rounded edges along its base surface.

Various forms of Karman vortex generators are used for flowmeters in which the vortices generated are used to create pressure differences on opposite sides of a vibrator plate whose frequency of rotation is measured optically as a measure of the fluid flow. One form of flowmeter, used to measure the quantity of air inhaled by an internal combustion engine, uses a chamber outside the path of the inhaled gas which is maintained at a negative pressure and which communicates both with the air line and outside air such that clean air is drawn in to keep the optics enclosed therein clean.

Karman vortex flowmeter

A Karman vortex flowmeter for deriving the velocity or quantity of fluid flow is comprised of an upstream pillar for producing Karman's vortex streets or paths that has a substantially isosceles triangle cross section, a downstream pillar for producing Karman's vortex paths that has a substantially isosceles trapezoidal cross section, a vibration chamber, and a vibrator member supported in the vibration chamber in a state of mass equilibrium relative to a revolving shaft passing through its center of gravity such that it can vibrate torsionally about the revolving shaft. The base of the upstream pillar is substantially equal to the base of the downstream pillar, and the pillars are positioned so that the bases are parallel to each other and perpendicular to the direction of the fluid flow. The vibrator member is preferably provided with a pair of taut bands supporting the vibrator member which form the revolving shaft and a frame which supports the bands. The taut bands may be pressed by a spring member to ensure uniform tension in the face of temperature changes, and may be damped with suitable elastic material. The flowmeter is provided with a photoelectric detector to detect the vibration of the vibrator member as it vibrates in response to pressure variations attributable to the Karman streets produced by the pillars. The detector preferably includes an integrator and comparator which cooperate to derive only effective frequency components.

In the particular embodiments of the invention described herein, a Karman's vortex flow metering apparatus has an oscillating plate magnetically held at the vertex of a triangular chamber located outside a flow line. Within the flow line a Karman's vortex generator is mounted transverse to the flow direction and has vortex generating slits extending along its length. Pressure detecting slits located at the end of the generator near the detector communicate through short pressure transmitting lines with opposite sides of the chamber. The resulting oscillation of the plate is detected optically or magnetically to provide signals corresponding to the flow rate.

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Kanagawa, Japan

Michihiko Tsuruoka