Abstract: Particle scattering is suppressed only by controlling the gate valve in opening the gate valve with the internal pressure of the chamber being matched to the atmospheric pressure.

Abstract: A Wellbore stress meter system and method for determining wellbore formation instability, comprising a first load cell, a first pressure sensor with a pressure output signal, a wireless communication system, a cable, and a surface device, said first load cell comprises; a second pressure sensor with a stress output signal, a cell element comprising a fluid, a first interface element in a first end of said first load cell with fluidly separated first and second surfaces wherein said first surface is in fluid communication with said fluid, and said first interface element moves relative said cell element as a function of a force applied on said first surface, and compresses said fluid acting on said second pressure sensor.

Abstract: A method for determining an environmental pressure change affecting a pressure sensor within a portable device to determine an elevation of the portable device is disclosed. The method involves sampling pressure data from at least one stationary pressure sensor in an area surrounding a location of the device, wherein the stationary pressure sensor in not within the portable device. The sampled pressure data is then interpolated to a time interval and a difference is computed between the interpolated pressure data over each time interval to determine a differential pressure. The location of the stationary pressure sensor is determined and the differential pressure is added to a pressure map affecting data near the location. The environmental pressure change is then computed over any interval at the location and subtracted from a pressure measurement of the pressure sensor before computing an elevation of the portable device.

Abstract: A system and method of measuring a residence time in a gas-turbine engine is provided, whereby the method includes placing pressure sensors at a combustor entrance and at a turbine exit of the gas-turbine engine and measuring a combustor pressure at the combustor entrance and a turbine exit pressure at the turbine exit. The method further includes computing cross-spectrum functions between a combustor pressure sensor signal from the measured combustor pressure and a turbine exit pressure sensor signal from the measured turbine exit pressure, applying a linear curve fit to the cross-spectrum functions, and computing a post-combustion residence time from the linear curve fit.

Abstract: Filling-level measurement device with a housing and a measurement cell arranged inside the housing, wherein the measurement cell comprises an essentially cylindrical measurement cell body, which comprises a membrane arranged crosswise relative to a longitudinal axis of the measurement cell body, wherein the measurement cell is mounted in the housing by a circumferential sealing element, which is arranged between the measurement cell body and the housing, wherein the sealing element is arranged in axial direction of the measurement cell in such a way that a measurement signal emitted by the measurement cell is independent from a compression of the sealing element.

Abstract: A method of determining the accuracy of a pressure sensor in a surgical cassette is disclosed. The method involves displacing a diaphragm of the sensor a pre-defined amount of displacement, and measuring the force exerted on the diaphragm by the displacing step. The accuracy of the pressure sensor is determined by comparing the force measured in the measuring step to a pre-defined force for the pre-defined amount of displacement.

Abstract: A testing apparatus for testing the level of retained gas at elevated pressure in plastic containers for carbonated beverages includes a manifold assembly for engaging the mouth of a test set of the containers. The apparatus additionally includes a gas supply for supplying a desired quantity of a selected gas to each container, the gas preferably helium. The apparatus further includes pressure measuring units for measuring the pressure in each container, and a data collection system coupled to the pressure measuring units for periodically collecting pressure data along with ambient temperature data as a function of time. The collected data can be analyzed to determine shelf life of the containers. Using helium, the shelf life determination can be accomplished in about {fraction (1/7)}th the time of conventional shelf life tests.

Abstract: An apparatus for measuring the differential pressure between at least two fluids including (a) first and second pressure enclosures; (b) first and second pressure deformable members where the first deformable member is sealingly connected to the first pressure enclosure and second deformable member is sealingly connected to the second pressure enclosure and the pressure deformable members are rigidly linked so as to move as one unit; (c) a frame for locating the first and second pressure enclosures in fixed relationship to one another; (d) a position sensing device for determining the displacement of the pressure deformable members relative to the frame; (e) a force balancing device including a first portion rigidly connected to the frame and a moveable second portion connected to the pressure deformable members; (f) a transducer for transducing the displacement of the first and second pressure deformable members into a force acting on the moveable second portion of the force balancing device in a direction t

Abstract: Determination is made as to whether or not a self-diagnostic tester 13 is connected with a K line 14. When the result of the determination indicates that the self-diagnostic tester 13 is not connected with the K line 14, data indicating vehicle-operating conditions are obtained from an engine ECU 11 and the like through a K line 14.

Abstract: An apparatus for measuring the differential pressure between at least two fluids including (a) first and second pressure enclosures; (b) first and second pressure deformable members where the first deformable member is sealingly connected to the first pressure enclosure and second deformable member is sealingly connected to the second pressure enclosure and the pressure deformable members are rigidly linked so as to move as one unit; (c) a frame for locating the first and second pressure enclosures in fixed relationship to one another; (d) a position sensing device for determining the displacement of the pressure deformable members relative to the frame; (e) a force balancing device including a first portion rigidly connected to the frame and a moveable second portion connected to the pressure deformable members; and (f) a transducer for transducing the displacement of the first and second pressure deformable members into a force acting on the moveable second portion of the force balancing device in a directi

Abstract: A pressure measurement and calibration apparatus for accurately detecting fluid pressures in the range of between approximately 0 and 1000 millitorr, and more particularly in the range of between 0 and 10 millitorr, and a method for calibrating an external pressure measuring device using the apparatus. The apparatus employs a pressure sensing assembly having a deflectable diaphragm and sensing electrodes. The assembly is rotated about an axis which is normal to the direction of local gravitational acceleration through preselected angles relative to the direction of local gravitational acceleration. The apparatus generates an output signal representative of the deflection of the diaphragm due to gravitational acceleration on the diaphragm at a given angular orientation. The apparatus then controllably conducts a fluid flow against the diaphragm at a sufficient pressure to substantially eliminate the deflection attributable to gravity on the diaphragm.

Abstract: A detector tube is supplied with air at an adjustable pressure balanced by at least two adjustable leak flow rates in the conduits 4 and 7 in order to adjust the position of ball in the tube. The possible manual inclination of tube between an extreme vertical position and position slightly inclined to the horizontal is a complementary means of adjustment. The detector tube can be used for the detection and measurement of micropressures and micro flow rates.

Abstract: An electromagnetic fluid pressure transducer is provided which uses the opposing magnetic fields of a permanent magnet and an electromagnet to sense a change in a differential force. The differential force is the result of a pressure applied to the unequal surface areas of two pistons attached to opposite poles of the permanent magnet. The differential force displaces the permanent magnet which activates a counter whose output controls the field strength of an electromagnet. The magnetic field of the electromagnet is varied by the counter output to counterbalance the differential force by interacting with the field of the permanent magnet. The field strength of the electromagnet is varied until the magnetic force is sufficient to overcome the differential force and return the permanent magnet to its original position which stops the counter. As a result, the counter output which changes in proportion to change in the ambient pressure acting against the pistons can be used to indicate pressure.

Abstract: A highly sensitive force detector using a tunneling junction as a strain gauge is disclosed. The tunneling junction is connected to a deflection member which receives the force to be measured. The junction is connected in a nulling circuit to a magnetic flux motor which generates a restoring force precisely equal to the force to be measured. The magnetic flux required by the flux motor to do so is measured by a SQUID, the output of which is directly proportional to the flux to be measured. The device has applications in pressure sensing, weighing, gravity measurements, detection of massive objects, and elsewhere.

Abstract: A method and apparatus for monitoring liquid levels using pressure responsive instruments is described, in which an arrangement for compensating for the effects of errors including gas weights errors is provided. The required compensation factor for a particular installation is first calculated theoretically, and then used in order to raise the output signal of the instrument electronically by the calculated factor. In one arrangement, the output signal is amplified by the desired factor. Alternatively, the excitation voltage of the instrument itself, or of a potentiometer used to interface the instrument to electronic data acquisition devices, is varied in order to raise its output voltage by the desired compensation factor.

Abstract: A null balanced fluidic sensing system that is less susceptible to pressure upply disturbances includes sensing and amplifying elements in a closed loop arrangement. The differential output of the sensor, developed as a result of an input stimulus, is fed into the inputs of a single sided amplifier. The output of the amplifier is used as a source of supply for the sensor. This closed loop arrangement uses the null offset characteristics of the elements to create a null balanced fluidic sensing system.

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 pressure measuring system which includes a pressure sensitive capacitor and a reference capacitor, a source of external excitation connected to the sensing capacitor, the reference capacitor being connected to a feedback signal generating circuit and the output from said capacitors being summed by a summing junction to produce an error signal. A phase sensitive demodulator is connected to receive the error signal and input same to a feedback signal generating circuit to generate the feedback signal for the reference capacitor. The feedback signal generating circuit includes a computing circuit for generating a digital signal corresponding to the magnitude of said feedback signal required to null said sensing capacitor signal to thereby provide a measurement of pressure.

Abstract: An improved pressure transmitter having a body with signal pressure responsive means and output pressure means having pressure responsive means, a supply of fluid pressure to said output pressure means, and adjusting means interposed between said signal pressure responsive means and said output pressure responsive means to adjust the force transmitted between said two pressure responsive means.

Abstract: A device is provided for the very accurate measurement of fluid pressures, comprising a vertical cylinder (2), a piston (1) adapted for sliding in this cylinder with viscous friction, the pressure to be measured being applied to the upper face (23) of the piston in an upper enclosure (22), means for rotating said piston in said cylinder, a precision electromagnetic dynamometric display balance (B) comprising a piece (3) to which the force to be measured is applied and means for transmitting to the piece of the balance the force applied to the piston by the pressure to be measured, with limitation of the maximum forces, a lower sealed enclosure (22a, 44A-44d), this lower enclosure being able to be evacuated or pressurized to a desired pressure (the atmospheric pressure or that of a fluid), and means for permanently supplying the clearance between the piston (1) and the cylinder (2) with fluid.

Abstract: Aircraft instrument for indicating air pressure, air pressure rate of change and accelerations of the aircraft movement based on the use of an optical laser interferometer. The air pressure is connected to one of several mirrors in the interferometer which causes the interference pattern to move up or down in response to the change in air pressure or acceleration. The interferometer uses a laser beam projected onto an optical detector that senses the motion of the interference pattern and produces a corresponding electrical signal which is connected to a linear motor which in turn is linked to the same mirror but in a negative feed-back arrangement that seeks to restore the position of the interference pattern. The amplifier output is an electrical analog of the atmospheric air pressure. The rate-of-climb is obtained by differentiating the amplifier output. The acceleration is produced by connecting the mirror to a mass.

Abstract: An improved back-pressured pneumatic pressure cell is provided along with a method of using the same. The device includes at least one sensing cell mounted on a blade for insertion into the soil. The cell includes a perforated outer ring and a perforated central disk separated by a threshold. A resilient membrane covers the outer ring and central disk. A first back-pressure is applied through the perforations of the outer ring to the membrane, while a second back-pressure is applied through the perforations of the central disk to the membrane. The second pressure is slightly less than the first pressure. When the first pressure reaches the soil pressure, the seal between the membrane and the threshold is broken, thereby permitting a momentary reverse flow of pressure through the perforations of the central disk until the first and second pressures equalize, as monitored by a differential pressure gauge. A valve regulates the pressure differential between the first and second pressures.

Abstract: The present invention is a pressure sensing and measurement device that eliminates errors due to compliance and lack of sensitivity. The cell uses a pressure receiving means (such as a flexible diaphragm) to detect an impinging object, a means to counteract the pressure caused by the impinging object (such as internal hydraulic pressure), and a detector to measure the amount of internal pressure used to counteract the impinging force. Since the cell is internally pressurized to a point equal to a value equal to the external pressure, the diaphragm is undeflected and may avoid the problems inherent in simple diaphragm systems (such as bridging and insensitivity).

Abstract: A device is provided comprising a circuit using the properties of a resonating cavity sensor whose resonance frequency is modified by the electric capacity variations due to the mechanical deformation of a wall under the effect of the pressure to be measured. It uses a single coaxial cable for connecting the sensor to the user circuit and the sensor, through the coaxial cable, is placed in the leg of an impedance bridge providing the value of the standing wave rate characteristic of the difference between the tuning frequency of the cavity and the frequency of an oscillator controlled by this rate.

Abstract: In a three force balanced mechanism comprising a floating pivot, an input force transmitting member, a feedback force transmitting member, one end of the input force transmitting member and one end of the feedback force transmitting member pivot in different directions, a flexible span setting member inclined with respect to the input force transmitting member, one end of the flexible span setting member being wound about or unwound from the floating pivot, there are provided detecting means for detecting the input force, restoring means responsive to the output of the detecting means for applying a restoring force to the feedback force transmitting member, and spring means for varying a force acting upon the input force transmitting member or the feedback force transmitting member in accordance with the movement of the free end of the span setting member.

Abstract: A pressure ratio measuring system is disclosed. The system includes two quartz capacitive pressure transducers (16, 22). Each capsule contains a pressure sensitive capacitor (Csa, Csf) which is fed by an alternating excitation signal. Capacitance (Csa) is fed by excitation signal (Vr) and Capacitance (Csf) is fed out of phase by feedback excitation signal (-Vr f(N)). The outputs of the capacitance are combined in a summing junction (36) whose output is an error signal (Ie) proportional to the pressure ratio. A feedback loop (26) is closed through a register (30) and a multiplying digital to analog converter (32) to generate the feedback signal (-Vr f(N)). The feedback loop (26) integrates the error signal (Ie) by incremental changing the feedback signal (-Vr f(N)) with digital number (N) in a direction to null the loop. When the loop is nulled the digital number (N) is a representation of the ratio (Pa/Pb) of the pressure (Pa) sensed by capacitance (Csf).

Abstract: A pressure translator for converting a process pressure into a pneumatic signal which can be transmitted and measured by a pressure measurement device at a remote location. The pressure translator provides isolation for the process and the measuring equipment but still translates the process pressure with very high accuracy. The pressure translator employs a balanced valve in cooperation with a forced balanced diaphragm.

Abstract: A circuit for coupling a transducer having a reactive sensing element to equipment providing either AC or DC drive voltage and equipped with strain gauge amplifiers in which the sensing impedance varies the gain of the feedback loop of an oscillator, an AGC circuit is coupled to the loop so as to derive a control signal related to the amplitude of oscillations therein and a gain control means is included in the loop that responds to the control signal in such manner as to restore the loop gain to unity after it has been changed therefrom by changes in the value of the sensing impedance. If the gain control means is a voltage divider having a variable resistor as the operative element, a matched variable resistor is used as the unbalancing element of a resistive bridge, and the values of the circuit are chosen such that the output signal from the bridge which may be applied to strain gauge amplifiers is linearly or desirably nonlinearly related to changes in the value of the reactive sensing impedance.

Abstract: A pressure parameter measurement system includes a parameter measurement loop (24, 16, 26, 28, 30, 32, 34) generating a digital signal (N1) indicative of a parameter (Pa-Pb) being measured, a common mode measurement loop (24, 22, 36, 38, 40, 42, Cfa) generating a digital signal (N2) indicative of an element (Pa) of the parameter (Pa-Pb), and a calibration circuit (46) which outputs the parameter (Pa-Pb) as a function of the digital signals (N1, N2) and a temperature signal T.

Abstract: A fluid pressure transducer of the null balance type in which a fluid whose pressure is being sensed acts against one face of a diaphragm and a balancing control fluid acts against the opposite face. Control fluid pressure is uniformly distributed against the control face of the diaphragm by a porous element, preferably made of a sintered material. Movement or displacement of the diaphragm opens a sensing element and may be controlled by use of a similar pressure distributing porous element placed on the sensing side. The volume defined between the two porous elements limits maximum diaphragm travel and displacement. Transducers made according to the invention have high sensitivity. The transducers are particularly well adapted for measurement of pore pressure in earth fills or natural geological environments.

Abstract: In a three force balanced mechanism of the type comprising a floating pivot, an input force transmitting member, a feedback force transmitting member, one end of these members being connected to the floating pivot and a flexible span setting member with one end secured to the floating pivot, the span setting member being inclined with respect to the input force transmitting member, the floating pivot has a cylindrical surface intersecting the two force transmitting members and one end of the span setting member is wound about or unwound from the cylindrical surface. In one embodiment the cylindrical floating pivot is formed a notch having side surfaces orthogonal to each other and the two force transmitting members are secured to respective side surfaces.

Abstract: A device for sensing and monitoring the pressure variations of a pressurized fluid in a duct (13), comprises an upper body (1) coupled to a pressurized air source (5) and a lower body (2) which is coupled by means of a resilient ring, to a sleeve (12) welded to the duct (13) in which the pressure is to be monitored. A graduated scale duct (18), associated with the upper body and communicating with a needle valve (16) affords the possibility of visually monitoring the adjusted air amount. A coupling duct (19) communicates with a joining duct (20), to which a pressure detecting instrument (22) is applied and leads to an interspace (23) defined between the lower and upper bodies and communicates in turn with the inner side of a diaphragm (26) which, on the opposite side, contacts the pressurized fluid.

Abstract: A differential pressure measuring system is disclosed. The system includes two quartz capacitive pressure transducers (14, 16). Each capsule contains a pressure sensitive capacitor (Csa, Csb) and a relatively pressure invariable reference capacitor (Cra, Crb). The pressure sensitive capacitors (Csa, Csb) are excited by out-of-phase signals, (Vr, -Vr) which further excite the reference capacitors (Cra, Crb), out of phase, respectively. The outputs of all capacitors are combined in a summing junction (22) whose output controls the count of a digital integrator (34). A closed loop is formed by converting the output of the integrator (34) to a negative feedback signal (lf) which is applied to the summing junction (22) through a feedback capacitor (Cf). The integrator (34) incrementally changes the feedback signal (lf) in a direction to balance the loop. At this point the output of the integrator (34) is representative of the measured differential pressure.

Abstract: A pressure ratio measuring system is disclosed. The system includes two quartz capacitive pressure transducers (16, 22). Each capsule contains a pressure sensitive capacitor (Csa, Csf) which is fed by an alternating excitation signal. Capacitance (Csa) is fed by excitation signal (Vr) and Capacitance (Csf) is fed out of phase by feedback excitation signal (-Vr f(N)). The outputs of the capacitance are combined in a summing junction (36) whose output is an error signal (Ie) proportional to the pressure ratio. A feedback loop (26) is closed through a register (30) and a multiplying digital to analog converter (32) to generate the feedback signal (-Vr f(N)). The feedback loop (26) integrates the error signal (Ie) by incremental changing the feedback signal (-Vr f(N)) with digital number (N) in a direction to null the loop. When the loop is nulled the digital number (N) is a representation of the ratio (Pa/Pb) of the pressure (Pa) sensed by capacitance (Csf).

Abstract: A digital system for measuring an input quantity includes an input mechanism for providing a first input in response to an input quantity to be measured, a stepper motor for providing a second input, a measuring apparatus connected to the input mechanism and to the stepper motor such that the measuring apparatus provides an output when the first and second inputs reach a predetermined relationship, and a circuit connected to the stepper motor and to the measuring apparatus for stepping the stepper motor from a reference position and for counting the steps of the stepper motor until the measuring apparatus provides the output.

Abstract: A pressure responsive switching device, particularly a pressostat or thermostat, comprises an actuating element (5) which is loaded in one direction by an operating element (1) at the pressure and in the other direction by a main spring (9) by way of a force transmission device (10). The latter has a physical quantity (P.sub.k) which is variable with the force transmitted by the operating element. In addition, there is a measured value generator (23) which, depending on this physical quantity, delivers an electric analogue signal (S). The force transmission device may comprise a compensating force producer (10) in the form of an expansion element (15) which is provided with a liquid-vapor filling and a heating device (21), by which the compensating force of the force of the operating element (1) is made to follow. In this way, the switching device can deliver an analogue signal (S) corresponding to the system pressure (P) by using the same operating element (1).

Abstract: A pressure transducer (26) is disclosed. A multiplicity of signal plates (Cs, Cr, Csf, Crf) are disposed on a first quartz disc (88). Opposing the signal plates (Cs, Cr, Csf, Crf) across a gap formed by an annular frit (92) is a common plate (94) disposed on a second quartz disc (86). The signal plates (Cs, Cr, Csf, Crf) and common plate (94) form capacitors which are operable to modulate alternating excitation signals applied to the signal plates. The capacitances vary the modulation during deflections of the discs (86, 88) as a result of pressure changes, and the common plate (94) algebraically sums the modulated excitation signals into a single output from the transducer (26).

Abstract: A force-balance pressure measuring instrument incorporates a fluid pressure couple. The couple constructively includes a fulcrumed beam. The primary element is connected to the force-balance beam through a proportional band adjustment having a leaf spring which is changed in effective length. At certain settings of the leaf spring in the proportional band adjustment, oscillations, or pulsations, of the fulcrumed beam are generated. A compensation beam is pivoted on the fulcrumed beam to respond to the pulsations or oscillations of the fulcrumed beam and absorb energy to reduce pulsations or oscillations.

Abstract: Low volume flow measurement apparatus developed for hearing dysfunction diagnosis but also suited to other applications comprises means (10) defining a cavity operably communicable with the variable volume, a D.C. microphone (15) responsive to ambient pressure changes in the cavity due to variations in said volume, and a reference diaphragm (17) operably connected with the cavity and moveable under servo-control responsive to the microphone to maintain the cavity pressure constant. The cavity will normally have a vent valve (18) and in non-hearing application may be coupled with the subject volume by a plunger seal. For hearing diagnosis the apparatus is suitably carried by a helmet (21) or harness with a headphone on the opposite side for sound stimulus application, the helmet itself being at one end of a boom (22) with a counterweight (23).

Abstract: A servo instrument, particularly a servo altimeter, with a minimum of display error. The instrument comprises a capsule assembly, a sector adapted for rotation corresponding to the displacement of the capsule assembly, a photosensor for producing an output showing its angular position relative to the sector, a support for rotating the photosensor while supporting it adjustably in a direction of tracing the sector, a cam adapted to make the amount of the adjustment of the photosensor variable by the position of the support, a motor, means for generating a signal showing the rotating positional angle of the motor, and an amplifier for amplifying the output of the photosensor and driving the motor so as to maintain the output of the photosensor constant.

Abstract: The pressure-measuring device comprises a first chamber subjected to the pressure to be measured and a second chamber connected to the first through an opening fitted with a valve. The device further comprises a valve-control circuit and an element for detecting the instants at which the pressure difference between the two chambers attains a predetermined increment or decrement or a zero value. The detection element consists of a deformable pressure-tight wall placed between the two chambers and adapted to produce action on an optoelectronic, piezoelectric or electromechanical element which converts the deformation directly to logical signals. A bidirectional counter is provided for forward or backward counting of the increments and decrements obtained.

Abstract: A circuit for measuring the reactance of an AC reactance sensor which varies responsive to a condition to be sensed, such as pressure, is disclosed. The circuit comprises an oscillator coupled to the sensor for providing a time varying oscillator signal having a variable frequency and a substantially constant peak to peak voltage to the sensor, and a plurality of rectifiers coupled to the oscillator and to the sensor for providing the oscillator signal as a charging signal to the sensor and for providing discharging signals from the sensor, the discharging signals being a function of the reactance of the sensor, and an amplifier coupled to the rectifiers and to the oscillator for providing an input control signal to the oscillator to control the frequency of the oscillator signal as a function of the reactance of the sensor.

Abstract: A differential pressure sensing device is fully implanted beneath the skin in the living body such that its pressure responsive means, such as a diaphragm means, senses the difference in pressure between an internal bodily pressure and the pressure on the skin which is just above the sensor. The sensor has a stop, or a mechanical contact means, for the diaphragm means so that the diaphragm will be pressed against the stop when an externally applied pressure on the skin equals or exceeds the internal pressure. The sensor also has a means with a detectable parameter that can be detected outside the body by external apparatus. The external apparatus also converts the parameter to an audible sound or audio signal. The parameter has a specific response when the diaphragm is near the stop position, and this response can be heard via the audio signal.

Abstract: A digital pressure measuring system with nonlinear resolution is disclosed. The system includes a capacitive pressure transducer with a pressure variable sensing capacitor and a substantially invariable reference capacitor. The capacitors of the transducer are excited by out-of-phase signals and their outputs combined at a summing junction. The output of the summing junction controls the incrementation of a counter whose output is converted to a nonlinear negative feedback signal. A closed loop is formed by applying the feedback signal to the summing junction through a feedback capacitor. The counter is incremented in a direction to null the loop such that its output is representative of the measured pressure.

Abstract: A device for converting a pneumatic or hydraulic pressure into an electrical current and vice versa according to the compensation principle, with a pressure transducer with a pressure-dependent moveable element, an electromagnetic force transducer, the moveable part of which force transducer standing in connection with the element, and a position indicator transmitter which converts the movement of the pressure transducer into an electrical or pneumatic control signal for the force- or pressure transducer. As a pressure transducer, there are provided two bellows with slightly different operative or effective surfaces which respectively are each fixed on one end and with their other ends stand in connection with one another and with the moveable element and are subjected to the same pressure.

Abstract: A balance beam has a fulcrum, at least one bellows (connected to a source of pressure or vacuum) acting on the beam and a connection to the armature of a differential transformer at one end. A poise is mounted for movement along the beam by rollers riding on shoulders formed on the beam. A carriage having a connection to the poise at the elevation of the axes of the rollers moves the poise and is, in turn, driven by a screw turned by a servomotor controlled by the differential transformer. Provision is made for minimizing temperature error both longitudinally and transversely of the beam. The fulcrum and bellows may be moved to different locations relative to the beam, using spaced drilled holes in the beam and the base plate. Various readouts may be connected to the screw, and recorders and control devices may also be driven by the screw.

Abstract: A balance beam has a fulcrum, at least one bellows (connected to the source of pressure or vacuum) acting on the beam at a point along its length and a connection to the armature of a differential transformer at one end. A poise is mounted for movement along the beam by rollers riding on shoulders formed on the beam in a unique arrangement. A carriage having a connection to the poise at the elevation of the axes of the rollers moves the poise and is, in turn, driven by an expansible belt, chain or cable extending around two sprockets, one of which is driven by a servo-motor controlled by a circuit including the differential transformer. Careful provision is made for temperature compensation both longitudinally and transversely of the beam yet the drive elements are elastic. The bellows may be moved to different locations relative to the beam by use of pre-drilled holes in the beam and base plate. Two bellows, on opposite sides of the fulcrum, may be used to gauge pressure differences.

Abstract: A differential pressure sensing device is fully implanted in the body of a patient to monitor internal pressure such as intracranial pressure. A movable element in the sensor communicates on one side with the internal pressure to be measured and on the other side with an external pressure which is applied by an external pressurizer-control system and which is communicated to the sensor through the intact skin. An imbalance of the two opposing pressures causes a displacement of the movable element which changes a physical characteristic of the sensor, such as the resonant frequency of a tuned L-C circuit. This change is detected outside the body by an external detection system, such as a frequency swept radio frequency oscillator. The external pressure is varied until the external detector senses that the pressures are balanced on the movable element, at which point the external pressure equals the internal pressure, and the former is measured and read out.

Abstract: A differential pressure sensing device is fully implanted in the body of a patient to monitor internal pressure such as intracranial pressure. A movable element in the sensor communicates with the internal pressure of the body to be measured on one side and the atmospheric pressure on the other, the latter communicated through the intact skin and a nearly coplanar membrane. The movable element's differential pressure dependent displacement changes a physical characteristic of the sensor, such as the resonant frequency of a tuned L-C circuit, and the change is detected external to the body by a radiating detector system, such as a frequency swept radio frequency oscillator, by which the internal pressure is read out.

Abstract: Apparatus for measuring barometric pressure comprising a housing made of high thermal conductivity metal and defining a cavity therein, a diaphragm of flexible spring type material clamped in position across the cavity dividing it into upper and lower portions, a connecting passage leading from the lower portion of the cavity to the pressure to be measured, electrical means for measuring deflections of the diaphragm and providing a control signal to a power supply, a low boiling point liquid filling part of the upper portion of the cavity in the housing, with vapor from the liquid filing the remaining part, a heating coil positioned in relation to the housing and connected to the power supply controlled by the electrical means such as to bring the temperature of the liquid and thus its vapor pressure to a level to balance the pressures across the diaphragm, thermal insulation encompassing the housing and means for measuring the temperature of the housing and the liquid therein, this temperature being related