Abstract: Pressure sensing devices which have a vibrating crystal or other load sensitive component responsive to external pressures and a reference component of the same character for outputting a signal which accurately reflects the magnitude of the external pressure and is obtained by ascertaining the difference between the sensing and reference components output signals. Preloading is employed in installing the sensing component, eliminating the need for bonding and/or mechanical connections and thereby reducing the cost of manufacturing and the potential error in output from the device. A component with a displaceable element such as a bellows or diaphragm is employed to preload the sensing component and to detect external pressure force, and provision is made for limiting the travel of the displaceable element so that the sensing of an external pressure exceeding design limits will not result in the sensing component being loaded to a level which might damage it or cause hysteresis.

Abstract: A vibrating sensor comprises an elongated element arranged to vibrate at a frequency dependent upon an external stress applied to the sensor, and an optical fiber for coupling light into an end of the element to excite it into vibration. A light-absorbing layer is provided on a longitudinal surface of the element such that the element will change its configuration, e.g. by bending, as the layer absorbs light and heats that side of the element, this alteration in configuration causing a reduction of radiation which is absorbed so that the element restores. The element may define a Fabry-Perot interferometer between its opposite ends.

Abstract: An acceleration sensor is used in particular for recognizing an impact experienced by a motor vehicle. The sensor has a spring-mass system (1) with at least one stable original position (4) and one stable deflection position (5). Upon acceleration in the measuring direction, the spring-mass system is initially deflected only slightly out of the original position (4). However, if a predetermined acceleration value is exceeded, then the spring-mass system (1) jumps into the deflection position (5), in which an electrical contact is closed.

Abstract: A pressure micro-sensor is formed by a sandwich of three silicon plates in contact by their periphery, with an interposed insulating layer in order to define an internal cavity. The lower plate (2) includes a thinner region (21) forming a diaphragm, on its internal side. The intermediate plate (1) includes a peripheral region (11) forming a frame coupled to the upper and lower plates by a silicon oxide layer (24, 25), a first stud (13) mounted onto the thinner region of the lower plate, a second stud (14) mounted onto a thick region of the lower plate, and a silicon beam (15) forming a resonator and disposed between the upper surfaces of the first and second studs in front of the upper plate (3). A first electrode (32) is connected to the upper plate, a second electrode (33) is connected to the frame and a third electrode (31) is connected to the second stud.

Abstract: A pressure measuring device comprises a pair of pressure compartments, a deflective structural element subjected to a force resulting from a differential pressure between two pressures respectively introduced into the two pressure compartments, and a pair flexible elongated members respectively anchored to and extending from the two opposite sides of the deflective structural element in two opposite directions, wherein one of the two flexible elongated members is anchored fixedly to a stationary support at its extremity, while the other of the two flexible elongated members is anchored to the stationary support in a spring biased arrangement that keeps the tension on the other of the two flexible elongated members constant; wherein a data processor determines the differential pressure between the two pressure compartments as a function of the natural frequencies of flexural vibrations of the two flexible elongated members.

Abstract: In pressure sensor systems based upon a micromachined silicon pressure sensor comprising a resonantly vibratable beam supported on a diaphragm, the beam is excited into resonant vibration by directing an optical excitation signal at the beam resonant frequency, via an optical fibre 26, onto a part of the sensor other than the beam, preferably the diaphragm. To detect the vibrations, the underside of the beam 16 and the adjacent upper surface of the diaphragm 18 are together arranged to define a Fabry-Perot cavity, and a continuous optical detection signal is directed at this cavity, also via the optical fibre 26. The optical detection signal is thus modulated at the vibration frequency of the beam 16 by the cavity, and the modulated signal is reflected back into the optical fibre 26.

Abstract: A unit which is useful in a measuring device such as a vibration rod transducer. The unit comprises supported diamond layers having an unsupported bridging diamond strip which is integrally formed with the supported diamond layers. The supported diamond layers may form part of a closed configuration such as a circle, square, rectangle or triangle. The diamond is preferably CVD diamond.

Abstract: A pressure microsensor comprises, between two plates in an insulating material: a bottom silicon plate (3) forming a base; a middle silicon plate (2) constituting a diaphragm (11) surrounded by a frame (12), a first part (15) of a stud being formed at a decentred location of the diaphragm; and a top silicon plate (1) comprising a frame (17) corresponding to that of the middle plate, a second parts (16) of said stud and a silicon blade (18) constituting a resonator connecting the top of the stud to a high area of the frame. A measuring interval (13) is provided between the diaphragm and the bottom plate, this interval comprising an access (14, 28), and the two insulating plates (4, 5) cooperate with the border of the three assembled silicon plates to form a closed cavity.

Abstract: A transducer for measuring a moment force as a related function of pressure and tension where a spirally wound bourdon tube has a confined end arrayed to apply a moment force to pretensioned metal vibratory elements. The change in tension in the pretensioned vibratory elements produces a change in frequency which is related to pressure in the bourdon tube. The vibratory elements are maintained at equally applied tension so that a temperature change changes the frequency of the vibrating elements and can be utilized to correct pressure measurements.

Abstract: A vibrating type pressure measuring device having good shock wave proof measuring characteristics, high frequency response, good temperature characteristics, and can be readily miniaturized, wherein pressure to be measured is applied to a silicon diaphragm provided in an internal vacant space of a housing, and a magnetic field is applied by a DC current magnetic field applying device to a vibrator beam arranged in the inside of the diaphragm, with a gap therebetween kept in vacuum, and fixed to the diaphragm at both ends, and detects the changes in natural frequency of the vibrator beam caused by the pressure to be measured. The diaphragm and/or vibrator beam are constructed so one or the other or both have rough or uneven surfaces so as to prevent any adhesion therebetween.

Abstract: A tensioned bellows pressure transducer having a pressure chamber [40], an elastic vibrating member [50], an electromagnetic coil [60] a linkage [33], a rigid body [30], a body extension [35], and a pressure deformable member [22] defining in part a reference chamber [20]. In preferred embodiments, the pressure deformable member is a bellows. Bellows [22] is attached at bellows fixed end [23 to rigid body [30] and is deformable in response to a difference between a bellows internal reference pressure p.sub.0 and any pressure p.sub.1 external to bellows [22], such as in pressure chamber [40]. Elastic vibrating member [50] is connected at a first end to linkage [33]. Linkage [33] projects rigidly from an interior face of bellows free end [24] and vibrating member [50] is connected to linkage [33] at a distance d.sub.2 from free end [24], and is connected to body extension [35] at a distance d.sub.1 from free end [24], where d.sub.1 is less than d.sub.2.

Abstract: In a micromachined silicon pressure sensor comprising a resonantly vibratable beam supported on a diaphragm, the beam is indirectly excited into resonant vibration by directing an optical excitation signal at the beam resonant frequency onto a part of the sensor other than the beam, preferably the diaphragm. Preferably, the optical excitation signal is of a wavelength to which the sensor is fairly transparent, and is directed through the beam and diaphragm to be absorbed by a suitable coating on the underside of the diaphragm. The optical excitation signal produces local heating, and the resulting expansions and contractions at the beam resonant frequency propagate through the sensor structure to excite the beam into resonant vibration. Another optical signal is used to detect the frequency of vibration of the beam, and a positive feedback loop maintains the frequency of the excitation signal equal to the detected beam vibration frequency.

Abstract: A micromachined silicon pressure transducer employs a vibrating bridge that is formed from the same silicon slab as the pressure responsive diaphragm. The resonant frequency of the bridge is a temperature insensitive representation of the pressure.

Abstract: A vibratory force transducer comprising a vibratory beam (21) of rectangular transverse cross section having a uniform thickness t, a major span section of length L.sub.1 and width w.sub.1, and at least one end of the major span having an adjoining tab of greater width W.sub.2 and length L.sub.s. The beam is driven by electrical excitation to vibrate at resonant frequency in a given direction. The tab provides the beam with an effective length which is a function of length of the beam sections and their moments of inertia in the given direction and a criterion by which t, w.sub.1, L.sub.1 and L.sub.s are selected such that resonant frequency and higher harmonic modes of the beam in the given direction are different from the resonant frequency and higher harmonics in any other direction. The transducer may comprise dual beams (31,32) as a double-ended tuning fork with moment decoupling number (45) at the joined end. For each beam comprising a major span of length L.sub.

Abstract: A differential pressure sensor comprises a pair of bourdon tubes disposed in an arrangement wherein deflections of the two bourdon tubes resulting from fluid pressures connected thereto take place in two opposite directions and the deflective extremities of the two bourdon tubes are linked to one another by a linkage, which linkage is coupled to a transducer that converts the displacement of the linkage to an electrical parameter such as the ohmic resistance, capacitance, reluctance, or resonance frequency as a measure of differential values between two pressures respectively connected to the two bourdon tubes.

Abstract: A force sensing assembly and particularly one which is especially suitable for use as a pressure transducer is disclosed herein. This assembly includes at least one and preferably a stacked pair of resonating type force sensing devices supported from one end in a cantilvered fashion.

Abstract: A vibrating type transducer wherein an H-shaped vibrator, formed integrally with a silicon substrate and having a hollow chamber provided therearound, is kept self oscillating at its natural resonance frequency together with an amplifier. A physical quantity, such as force, pressure, differential pressure, or the like, which is applied to the silicon substrate is detected by a change in the natural frequency arising at the vibrator corresponding to the physical quantity. The invention also includes a method for manufacturing such transducer using a semiconductor technique, including steps for keeping a vacuum internally in the hollow chamber, imparting an initial tension to the vibrator, and then operating the amplifier to have stable self oscillation.

Abstract: This invention discloses a differential or absolute pressure sensing apparatus that measures pressure exerted on a mechanical pressure sensing element in digitized electrical signals, which comprises two pressure receiving compartments separated from one another by a diaphragm or disc secured to two tension wires extending therefrom in two opposite directions and anchored at two extremities thereof, wherein electromagnetic vibrators intermittently induce vibration of the tension wires and vibration detectors measure the natural frequencies of vibrations of the two tension wires. The difference in pressures on two sides of the diaphragm or disc is proportional to the difference in the square of the natural frequencies of the two tension wires and, consequently, the differential pressure across the diaphragm or disc is obtained by measuring the natural frequencies of vibrations of the two tension wires. When one side of the diaphragm or disc is evacuated, the absolute pressure is measured.

Abstract: A fluid mass flow sensor uses the effect of aerodynamic drag on a vibrating object. The drag damps the resonance oscillations of the vibrator in an amount proportional to the mass flow. An electronic feedback circuit associated with the mass flow sensor has the effect of allowing for fast response time despite the use of a high Q vibrator and allows for electronic calibration of the device.

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: In a transducer, e.g. a pressure transducer, the sensing element comprises a torsional oscillator provided with magnetic means for feedback of signals to maintain oscillation. Typically the sensing element is formed by selective etching from a body of single crystal silicon.

Abstract: A pressure transducer 10 is disclosed wherein a bellows 11 is expanded by an external pressure applied at pressure port 16. The force created by external pressure applied to bellows 11 is mechanically transferred to one end of a vibrating elastic member 14 by axial displacement of saddle 13. A change in external pressure is thereby read as a change in resonant frequency of elastic member 14.

Abstract: An apparatus for sensing differential pressures is provided. The apparatus includes a housing having an inner chamber filled with an incompressible working fluid. First and second diaphragms are provided in said housing for interacting with the fluids being measured. A flex-tube is provided in the housing and is coupled to one of the diaphragms for sensing the differential pressure. One end of the flex-tube is securely mounted to the housing and the other end is coupled to the diaphragm. A quartz sensor is positioned on the core for sensing strain applied to the flex-tube by the differential pressure exerted on the diaphragm.

Abstract: A vibratory transducer comprising a vibratory beam composed of an n-type layer and having at least one end fixed. The vibratory beam is formed by selectively etching an n-type layer formed by adding impurities locally to a single silicon crystal. The vibratory transducer also comprises means for vibrating the vibratory beam and means for detecting vibration of the vibratory beam. The vibratory transducer measures pressure, temperature, density, etc, by detecting change in the resonant frequency of the vibratory beam. The vibratory beam can be finely etched irrespective of the density of the impurities therein by forming the vibratory beam in an alkaline aqueous solution while applying a negative DC or pulsed voltage to a p-type layer and a positive DC or pulsed voltage to an n-type layer. The vibrating and detecting means for the vibratory beam can be easily provided by making a diode and a transistor including the vibratory beam in the transducer.

Abstract: Microminiature resonant sensor structures are prepared according to micromachining/microfabrication techniques, which structures include thin-film deposits of piezoelectric materials. Such piezoelectric deposits may be excited electrically by including metallized conductive paths during fabrication, or optically. The resonant frequency of the sensor structure is varied by subjecting it to a physical variable, or measurand, such as pressure, temperature, flow rate, etc. Similarly, the resonant frequency of the devices may be detected electrically or optically. The microminiature resonant structures include ribbons and wires, hollow beam and cantilevered hollow beams, and single- and double-ended double beam resonant structures such as tuning forks.

Abstract: A pressure sensor uses two fluidically coupled piezoelectrically driven, vibrating cantilever structures, each tuned to the same fundamental resonance frequency. One cantilever, the driver, is electrically driven at resonance and at constant vibrational amplitude. The other cantilever, the receiver, responds due to the gaseous coupling and generates an output signal proportional to pressure.

Abstract: A digital differential pressure sensor with relatively low sensitivity to common mode line pressure errors. The sensor includes an airtight enclosure having a pair of pressure ports through which pressures are coupled to opposite sides of a pressure-sensing diaphragm, bellows, or Bourdon tube. The pressure-sensing elements generate torques which are transmitted by a shaft to stress-sensitive resonators which are isolated from the torque-producing elements by a sealed, flexible tube.

Abstract: A microminiature resonant hollow beam sensor is manufactured by micromachining and microfabrication techniques. Specifically, a sensor is formed by etching troughs in a pair of silicon substrates, joining the substrates face-to-face, and etching away unwanted material to free the resonant hollow beam sensors.

Abstract: An apparatus for measuring pressure within a conduit is disclosed preferably comprising a tube whose resonant frequency varies with the pressure of fluid within the tube; means for passing the fluid to be measured through the tube; two active piezoelectric films disposed in intimate contact with the tube on opposite sides thereof; first electronic means for energizing the first of the films to cause the tube to resonate at its natural frequency, and second electronic means connected to the other of the films to monitor the frequency of the tube.

Abstract: A differential pressure gauge comprises a balance beam (3) acting upon a vibrating blade (6). The beam (3) and the blade (6) are disposed in a rigid chamber 4 under vacuum. The beam (3) is acted upon by a force, resulting from the deformation of a flexible or expansible chamber (7) subjected to a pressure P.sub.T and disposed in a second rigid chamber (5) subjected to a pressure P.sub.S. A flexible or expansible seal element (9) isolates the chambers but transmits the forces without disturbing them. This gauge has a high precision and delivers information in digital form, particularly useful in aeronautics.

Abstract: A process control instrument, in which the resonant frequency of a vibrating string varies in accordance with changes in a process parameter being monitored, employs a pneumatic drive system to induce the string into oscillation. Pressurized gas is discharged through a port, such as a jet nozzle, which is disposed to allow the gas to impinge on the outer surface of the string. Variations in the alignment between the gas discharge port and the string permits different modes of vibration, one of which is particularly suitable for process measurement purposes. In a particular embodiment of the apparatus, an optical sensor detects the frequency of vibrations, resulting in an intrinsically safe instrument for use in explosive environments.

Abstract: A digital pressure transducer is formed by mounting a force-sensitive resonator to a structure of nonsymmetrical configuration which produces loads under applied pressure. The frequency of the resonator is measured to provide a digital indication of the applied pressure.

Abstract: A cast string-type measurement cell, including a metallic string member having cast thereto nodal masses, clamping elements, and spring and suspension elements, thereby to define an integral structural assembly that may be formed by a casting mold in substantially finished condition ready for installation in the measuring apparatus. Preferably, the string is formed of an amorphous metal, and the cast components comprise a glass-fiber-reinforced synthetic plastic material.

Abstract: In a vibrating vane pressure gauge in which a plane metal vane is vibrated in an enclosure of only slightly larger area than the vane and the decay of the vibration (which is proportional to gas pressure) is sensed, the vane is provided with at least one lip along an edge of the vane.

Abstract: A fluid pressure gauge comprises a unitary, sealed, U-shaped hollow tube (12) with an electrically conductive ribbon (14) stretched between the ends of its arms (18). Fluid pressure applied to the interior of the tube via an inlet (24) on the axis of symmetry tends to straighten the tube, thereby varying the tension in the ribbon. The tension, and thus the pressure, are sensed by measuring the natural frequency of electromagnetically-maintained transverse vibration of the ribbon. Adjustment of the initial tension of the ribbon enables temperature sensitivity of the gauge to be reduced. One arm of the tube can be omitted, the ribbon being connected chordally across the curved portion and the pressure being applied through the remaining arm, or alternatively the tube can be serpentine in form.

Abstract: An instrument for developing at a central control station a signal responsive to the value of a process condition occurring at a field measurement station remote from the central control station wherein a resonant device is used as the instrument basic sensor element. The resonant device which is located at the field station may be excited by either a voltage pulse or a continuous wave. In a particular aspect, the output measurement signal of the instrument is solely dependent upon the value of a desired measured variable, which is representative of a process condition, and is independent of other variables. The resonant device is coupled to excitation and detection circuitry located at the central control station and produces in the detection circuitry when excited with a pulse of energy first and second signals, one of which is dependent upon the desired measured variable and a second variable and the other dependent upon at least the second variable.

Abstract: A pressure sensor and sensing method, wherein the sensor comprises a pressure responsive element movable corresponding to a pressure to be measured and a means for detecting movement of the pressure responsive element. The movement detecting element comprises two parts of switch means movable to and fro with respect to each other, and a substantially constant oscillation is applied to one part so that movement of the pressure responsive element alters a threshold value which is applied to the substantially constant oscillation in order to produce a varying pulse signal.

Abstract: The method of making a force-responsive instrument of the type including a tensioned wire of round cross-section to be vibrated perpendicular to the wire axis, wherein said instrument includes field-producing magnetic means operable with said wire to induce vibration; said method including the steps of:positioning said wire in a magnetic field directed perpendicularly to the wire axis;vibrating said wire by electrical means connected to the wire and arranged to develop interaction with said magnetic field;developing an electrical signal proportionately responsive to the magnitude of vibrations of said wire;effecting relative rotation between said wire axis and said magnetic field while maintaining constant the intensity of said magnetic field;making measurements of the amplitude of the signal developed by said wire;determining from said measurements the position of said wire relative to said magnetic field providing maximum signal amplitude; andfixing said wire in said instrument in said position relative to

Abstract: A sensor providing an output indicating pressure including means to excite a vibrating beam at its natural frequency, and means to load the beam in response to pressure to alter the natural frequency of the beam. The frequency output is sensed by a capacitor pick off mounted on the same side of the beam as the means to excite the beam. Changes in the output frequency provides an indication of the pressure being measured.

Abstract: A digital pressure sensor for measuring fluid pressures at relatively high temperatures includes an electrically conducting fiber coupled to the fluid by a force disc that causes tension in the fiber to be a function of fluid pressure. The tension causes changes in the mechanical resonant frequency of the fiber, which is caused to vibrate in a magnetic field to produce an electrical signal from a positive-feedback amplifier at the resonant frequency. A count of this frequency provides a measure of the fluid pressure.

Abstract: A silicon transducer including a silicon frame with one or more lands extending from a diaphragm or the like. The lands are interconnected by two thin strips formed integrally with the lands. The strips are essentially the transducer. The transducer is constructed by etching a boron doped wafer with a mixture of catechol, ethylene diamine and water.

Abstract: A pressure measuring instrument of the vibrating-wire type comprising an elongate base on which is pivotally mounted an elongate lever parallel to the base. A vibratory wire in the form of a very thin flat ribbon of tungsten is held tautly between the lever and the base. A pair of bellows are supported on the base, on opposite sides of the pivot mounting for the lever, and apply a torque to the lever proportional to differential pressure. Counterbalance means are provided to prevent errors with changes in spatial orientation of the instrument. The lever support-structure is formed of a composite of elements providing a match of temperature expansion characteristics with the vibratory wire. An overrange protection mechanism prevents the application of excessive force to the wire.

Abstract: A differential-pressure measuring instrument comprising a main body assembly with a pair of diaphragms each subject to a respective fluid pressure. The diaphragms enclose a sealed chamber containing a fill-liquid surrounding a non-magnetic vibratable wire which is tensioned in accordance with the applied differential pressure. A magnetic field passes transversely through the wire, and electrical current is supplied to the wire by electronic circuit means to produce a vibratory force on the wire as a result of interaction between the electrical current and the magnetic field.

Abstract: A differential-pressure measuring instrument comprising a main body assembly with a pair of diaphragms each subject to a respective fluid pressure. The diaphragms enclose a sealed chamber containing a fill-liquid surrounding a non-magnetic vibratable wire which is tensioned in accordance with the applied differential pressure. A magnetic field passes transversely through the wire, and electrical current is supplied to the wire by electronic circuit means to produce a vibratory force on the wire as a result of interaction between the electrical current and the magnetic field.

Abstract: A differential-pressure measuring instrument includes a pair of diaphragms each subject to a respective fluid pressure. The diaphragms enclose a sealed chamber containing a fill-liquid surrounding a non-magnetic vibratable-wire which is tensioned in accordance with the applied differential pressure.A temperature compensating inductor is connected in parallel with the vibratable-wire to compensate for variationsin the vibrating frequency of the wire due to changes in the viscosity of the fill-liquid with temperature.

Abstract: A pressure measuring instrument of the vibrating-wire type comprising an elongate base on which is pivotally mounted an elongate lever parallel to the base. A vibratory wire in the form of a very thin flat ribbon of tungsten is held tautly between the lever and the base. A pair of bellows are supported on the base, on opposite sides of the pivot mounted for the lever, and apply a torque to the lever proportional to differential pressure. Counterbalance means are provided to prevent errors with changes in spatial orientation of the instrument. The lever support-structure is formed of a composite of elements providing a match of temperature expansion characteristics with the vibratory wire. An overrange protection mechanism prevents the application of excessive force to the wire.

Abstract: A magnetostrictive pressure transducer is disclosed wherein pressure in the range of zero to 1000 psi can be accurately measured. The pressure transducer apparatus includes a diaphragm causing the pressure to be applied unidirectionally on sensor material having the property of undergoing changes in magnetic induction when a pressure is applied thereto, the change in magnetic induction being related to the applied pressure. The change in magnetic induction is measured and thus provides a measurement of the applied pressure. Several embodiments are also disclosed for measuring vacuum. In these embodiments force is also applied unidirectionally on the sensor material.