Abstract: A remote seal-type pressure signal generator has a pressure measuring end having a sealing diaphragm facing a pressure to be measured, a pressure detector body connected to the pressure measuring end through a first capillary tube, the detector body having a pressure-receiving space in which a pressure transmitting medium is liquid-sealed and pressure detecting means for detecting an internal pressure of the pressure-receiving space by way of a pressure difference thereof with respect to a pressure of a second pressure-receiving space to which a second pressure is applied, and a flexible protective pipe covering the capillary tube between said detector body and said pressure measuring end, a second capillary tube is housed in the protective tube, and extending from the second pressure-receiving space in the detector body while having substantially the same length as the first capillary tube, and having a distal end closed in the vicinity of the pressure measuring end, with the pressure transmitting medium bei

Abstract: The high pressure sensor includes a housing part, a lid closing the same and an intermediary disposed sensor disk. A cylindrical pressure chamber is formed in the housing, wherein an inner area of the sensor disk is disposed in a sealed off manner. In this area the measuring sensors are disposed in form of piezoresistive layer resistors. Layer conductors penetrate from this inner area into an outer area, wherein evaluation circuits and the evaluation electronic are disposed. The total sensor disk is provided with one or a plurality of glass layers in such a manner that a flat surface is obtained. Pressure changes of the pressure medium are picked up in the pressure chamber by the measuring sensors and are processed accordingly. Such a high pressure sensor is relatively simple and advantageous in its use.

Abstract: A pressure transducer system which uses a Wheatstone bridge circuit to produce an electrical signal which is proportional to the amount of pressure exerted on it by gas or liquids, is disclosed. The Wheatstone bridge circuit is thermally isolated from the external environment using two diaphragms which are separated by a reservoir of silicone oil. This allows pressure to be hydraulically conveyed to the Wheatstone bridge circuit while preventing thermal contamination of the electrical signals produced by the Wheatstone bridge circuit. The pressure transducer also contains support circuitry which allows adjustment of the signals to and from the Wheatstone bridge circuit to enable the pressure transducer to be used with various electrical measuring equipment which has different operational ranges.

Abstract: The present invention relates to a pressure reducing instrument for pressure gauges and includes a cylinder and a piston operable within the cylinder. The piston is designed with a pressure receiving face and a pressurizing face, and includes a plunger fixed on an end portion of a piston. An intermediate member having an atmospheric introductory aperture which penetrates through the plunger and leads to the piston is secured to the cylinder, the introductory aperture being open in an end face portion of the plunger. The instrument further includes a pressure transmitting fluid-retaining portion maintaining the pressure transmitting fluid, a detecting rod penetrated through by an introductory aperture and being received in the pressure transmitting fluid-retaining portion and a clamp member being tightened to the cylinder by a bolt through a rod seal.

Abstract: A differential pressure transmitter has a body wherein a pressure transmission passage filled with a pressure transmission medium is formed. A differential-pressure/displacement converting element is disposed in the body to partition the passage into a high-pressure side section and a low-pressure side section. A first seal port through which the transmission medium is charged into the high-pressure side section and a second seal port through which the transmission medium is charged into the low-pressure side section are formed in the body. First and second throttle members capable of being taken out through the seal ports are disposed in the high- and low-pressure side sections to throttle the sections.

Abstract: A pressure transducer with a diaphragm coupler at one end and a sensing element at the other end connected by a capillary tube. The sensing element includes a cap member having a deformable surface including a top wall forming a thin diaphragm having a diametrically disposed raised beam extending across the top surface and having a gage received surface for receiving a plurality of strain gages. The deformable top wall surface has indentations therein on either side of and extending longtudinally of the raised beam to reduce tension forces across the diaphragm and improve linearity of the diaphragm.

Abstract: A pressure transducer with a diaphragm coupler at one end and a sensing element at the other end connected by a capillary tube. The sensing element includes a cap member having a deformable surface including a top wall forming a thin diaphragm having a diametrically disposed raised beam extending across the top surface and having a gage receiving surface for receiving a plurality of strain gages.

Abstract: Extinguisher provided with a temperature compensated pressure controller, comprising a propelling agent and an extinguishing agent under gaseous form, wherein it comprises a sealed chamber filled with a mixture having a thermodynamic characteristic similar to that of the two agents in the extinguisher, a system for measuring the differential pressure exisiting between the inside of the sealed chamber and the chamber per se and a device actuated by the system for measuring the differential pressure and generating an alarm signal when the differential pressure exceeds a threshold value.

Abstract: A differential-pressure instrument the body of which forms a sealed interior pressure chamber containing a fill-liquid and includes a pair of flexible diaphragms to apply to the fill-liquid an input differential pressure to be sensed by an IC strain-gauge chip within the chamber. A spring plate divides the interior pressure chamber into two sections and is deflectable in response to differential pressures. Overrange pressure protection is provided by a valve which is closable by an elastomeric pad carried by the spring plate when the plate deflection reaches a pre-set amount. Valve closure locks the fill-liquid in place alongside the plate to provide an incompressible liquid back-up preventing further deflection of the plate, thus preventing further increases in differential pressure across the IC chip. In one embodiment, valves are placed on both sides of the spring plate to protect against both high-side and low-side overrange pressures.

Abstract: A fluid filled force or pressure sensor for measuring an external force such as a fluid pressure. The apparatus includes a housing having a substantially planar backup surface, a flexible diaphragm having its radially outer portion sealed to the backup surface of the housing. A variable volume fluid chamber is formed between the backup surface and the diaphragm and is filled with a pressurized working fluid causing the diaphragm to flex outwardly away from the backup surface. The apparatus also includes a sensor chamber formed in the housing and in fluid communication with the variable volume fluid chamber. Mounted within the sensor chamber is a means for sensing variations in the density of the working fluid within the sensor chamber, such variations in density being caused by flexing of the diaphragm as a result of variations in the external pressure to be measured.

Abstract: A solid state semiconductor pressure sensor is described in which the pressure sensor element is protected from the ambient whose pressure is being measured by a combination of a pressure transfer medium and a thin covering membrane. A method is described for applying the thin covering membrane so as to substantially avoid entrapment of air or formation of voids in the pressure transfer medium which would degrade the performance of the sensor. The pressure transfer medium is a gel-like material such as a silastic. The membrane is chosen to be substantially impermeable to the ambients being measured and sufficiently flexible to be rolled across the surface of the assembly during fabrication and to avoid attenuation of the input pressure signal. Fluorosilicone is an example of a suitable membrane material.

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 pressure probe for an arc furnace having a roof provided with an access opening. The probe is located above the opening and includes side and end walls defining a bottom periphery for sealing the opening and an upper periphery which is sealed by a removable cover. The open cover and side walls are releasably secured in surrounding relation to the furnace roof by cross bars and threaded tie rods. A plurality of holes are formed in each of the side walls and each hole is adapted to be coupled to a conduit for communicating a pressure measuring device to the openings. A baffle is fixed to each side wall and is disposed between the opening and the holes to shield the holes from any direct line of sight from within the furnace but does not prevent pressure communication between the furnace interior and the holes.

Abstract: An improved differential pressure transducer is provided having static overpressure protection means. The overpressure protection means includes spring-loaded element being shiftable in response to an overpressure condition.

Abstract: A measuring diaphragm (1) separates in a pressure-tight manner two half chambers (9, 10) suitable for being respectively subjected to two pressures to be compared. In a central zone of the diaphragm (1) there are two magnetic cores (118, 127) which are disposed on opposite sides of the diaphragm in respective ones of the half chambers and which are displaced with the diaphragm when the faces of the diaphragm are subjected to different pressures. The cores are movable inside respective simple inductors (132, 133 ), thereby varying their impedances. By measuring this impedance variation it is possible to determine the position of the cores in the associated inductors, and consequently to establish the difference between the pressures being applied to respective faces of the measuring diaphragm (1). The above arrangement provides for automatic zero correction in an inductive differential pressure sensor.

Abstract: A Venturi tube which is especially suited for the differential pressure measurement of flowing gas/particulate material media with high dust loading at temperatures exceeding 100.degree. C. and at elevated pressures includes a pressure-resistant metallic jacket and an inner lining of wear-resistant porous material which is accommodated in the jacket and bounds a flow-through passage with the Venturi configuration. Respective annular chambers are situated at the inlet region and at the smallest-diameter region of the flow-through passage, there annular chambers being separated from the flow-through passage by respective layers of wear-resistant porous material and being connected by respective pulse conduit with a differential pressure measuring device.

Abstract: A physiological pressure measuring system usable in conjunction with an intravascular infusion line leading to a patient whose pressure is to be monitored. The system includes a detector having a transparent chamber interposed in the line and a flexible bulb mounted therein whose exterior is subjected to the fluid pressure in the chamber, the bulb interior communicating with a flexible pipe terminating in a hollow plug vented to the atmosphere whereby the bulb is caused to collapse when the infusion fluid pressure which reflects the physiologial pressure is greater than atmospheric. Associated with the detector is a fluid pressure transducer yielding a signal as a function of the applied pressure, the transducer input port being in the form of a tubular jack adapted to telescopically receive the plug. When the plug is inserted in the jack, a seal is effected to create a closed air column which exerts pressure on the transducer.

Abstract: A semiconductor strain-gage is disposed in a recessed chamber of a housing. A step is provided in the recessed chamber. Minute grooves are provided in the inner peripheral portion of the step. An outer periphery of a metal disk with a pressure introducing bore is clamped to the minute grooves by means of plastic deformation thereof, after the seal diaphragm is disposed on a planer portion of the step, whereby the seal diaphragm closes the recessed chamber harmetically.

Abstract: A pressure measuring apparatus especially of aggressive fluids includes a manometer whose casing accommodates a diaphragm separating a first chamber within the casing from a second chamber within the casing. The first chamber contains a neutral fluid which transfers the pressure of the aggressive fluid provided in the second chamber and exerting a pressure onto the diaphragm to a mechanical indicator of the manometer for indicating the measured pressure.

Abstract: A pressure sensor has a housing in which at least two diaphragms are secured in such a manner that they include a volume which is filled with a hydraulic fluid. The incompressible hydraulic fluid serves to transmit pressure between the diaphragms. For introducing the hydraulic fluid one diaphragm is provided with an opening. A narrow tube is connected in fluid-tight manner to the edge of the opening. The hydraulic fluid is introduced through the initially still open end of the narrow tube. After the filling with hydraulic fluid the open end of the narrow tube is sealed in fluid-tight manner, for example by squeezing. The narrow tube can serve at the same time a force-transmitting or travel-transmitting member which connects the diaphragm to a force or travel sensor.

Abstract: A pressure difference measuring device having a semiconductor pressure sensor in a pressure pickup body which supports at each end face thereof a separating diaphragm with an adjacent supplemental diaphragm. On both sides of the semiconductor pressure sensor, a connecting canal is provided which leads in spur canals to the separating diaphragms and the supplemental diaphragms. In order to equip a pressure difference measuring device of this type with mechancial damping without adverse consequences for the operation of the overload protection, a damping element is arranged in at least one connecting canal. An equalizing diaphragm is associated with the semiconductor pressure sensor, the two sides of which are connected by the connecting canals in the region between the semiconductor pressure sensor and the damping element.

Abstract: A movable piston is supported by a flexible angular membrane around the perimeter of the piston in a piston chamber, having opposed walls which confront the opposite faces of the piston. The chamber has low and high pressure sides at said opposite sides of the piston. The potential movement of the piston is limited by contact of the piston face with the chamber wall, with the entire resistance to piston movement beyond the limit point being born by the chamber. The piston controls activation of an electric switch in response to movement of the piston.

Abstract: A pressure transducer comprising an elongate hollow outer housing having a pressure sensor diaphragm and externally positioned fixing means which facilitates pressure tight introduction of the diaphragm into a pressure sensing port provided in apparatus capable of generating pressures to be sensed, two elongate members positioned within the outer housing in operative association with the diaphragm so as to move differentially in a direction parallel with the longitudinal axis of the housing consequent upon movement of the diaphragm responsively to a pressure to be sensed, and transducer means responsive to differential movement between the elongate members for producing a signal in dependence upon the pressure sensed.

Abstract: The invention involves the design of a piezoelectric pressure transducer d for measuring pressure-time characteristics in gun tubes during the propellent ignition and burning process. The transducer utilizes one or two Z-cut tourmaline crystals as the piezoelectric pressure sensing element which produces a finite amount of electrical charge for a given change in pressure. The tourmaline crystals are incapsulated in a mechanical fixture which provides means for mounting in the gun tube, electrical terminals for connecting to signal conditioning and recording instrumentation, and insulators for electrically insulating the transducer from the weapon ground. A needle valve is also incorporated in the transducer which provides means for replenishing the thermal protecting material around the crystal assembly without removing the transducer from the weapon.

Abstract: A pressure gage particularly suitable in a variable temperature environment includes a body carrying two force rods. One of the force rods is coupled to the source of pressure to be measured while the second, of similar length and parallel to the first, is separated from the pressure to be measured. The total strain on both rods is affected by the same factors except that the rod coupled to the source of pressure is also affected by that source of pressure. When the strain of the two rods are subtracted the resultant strain is attributed only to the measured pressure.

Abstract: A pressure transducer which includes a novel apparatus and method for calibrating a pressure transducer to a monitor used in connection with an indwelling catheter to monitor a patient's blood pressure. The pressure transducer includes a transducer diaphragm disposed within a housing cavity. A manometer and a syringe are connected so as to be in communication with the transducer cavity. By partially withdrawing the plunger of the syringe, the pressure in the transducer cavity is reduced, thereby establishing a pressure drop equal to that measured by the manometer across the transducer diaphragm, thus facilitating calibration of the pressure measurement system. Inasmuch as the indwelling catheter is isolated from the pressure calibration apparatus, the methods and apparatus of the present invention avoid any risk of introducing air bubbles or microorganisms into the indwelling catheter.

Abstract: A pressure transducer (10) in which a sensor beam (14) is connected to a diaphragm (18) by a shaft assembly (120) which is made up of a sensor post (122) attached to the sensor beam (14), an overpressure stop member (124) attached to the diaphragm (18), and a rigidifying material (126) connecting the sensor beam (14) to the overpressure stop member (24) is disclosed. The overpressure stop member (124) is formed with an extended hollow cylindrical portion (125) that surrounds the sensor post (122), and the rigidifying material (126) fills the space between them.

Abstract: A differential pressure transducer assembly for measuring flow in dirty and solids bearing fluids utilizes small barrier diaphragms located at the pressure taps of a flow measuring restriction. The barrier diaphragms are of minimum size and minimum thickness with a minimum volumetric compliance and are connected to a pressure receiving body by equal length capillaries of minimum i.d. A measuring transducer with a diaphragm having low volumetric displacement for measured differential pressures and having minimum volume diaphragm cavities is connected to the capillaries by equal and minimum volume cavities in the pressure receiving body.

Abstract: A pressure gauge includes a cylindrical member having a flexible plate covering one end. Center flex of the plate is used to measure the force applied by fluid pressure. A low pressure transducer electrically measures the applied force. Pressure is transmitted from the flexible plate to the transducer by hydraulic fluid enclosed in the cylinder by a plastic boot. The boot is sealed to the cylinder by a sweat fit between the cylinder and a coaxial collar. The range of forces that can be measured is controlled by the thickness and diameter of the plate. In addition to pressure, the gauge can be used to measure temperature and orifice opening, and provide an indication of volumetric flow of the fluid.

Abstract: A pressure measuring device wherein a housing (1) includes a pressure sensor (2) in a pressure chamber (4) and an electronic circuit (14) in a non-pressurized chamber (6). Borings (7) extend between pressure chamber (4) and non-pressurized chamber (6) and accommodate contacts that electrically connect pressure sensor (2) and electronic circuit (14). A pressure membrane (3) cooperates with housing (1) to further define pressure chamber (4) and isolate the device from the fluid system. Pressure chamber (4) is filled with a medium that transmits the system pressure to pressure sensor (2). Pressure sensor (2) measures the pressure and provides an output signal to electronic circuit (14).

Abstract: A transducer for sensing pressure has a first and a second pressure chamber for sensing pressure and a center stop which has two substantially flat faces, each face cooperating with an associated sensor diaphragm which forms the first and the second pressure chamber. The two chambers are fluidically coupled together. Each of the diaphragms is responsive to a pressure P1 or P2 respectively and the transducer is easily configured to sense differential, gage or absolute pressure. When the pressure to be sensed exceeds a predetermined value the affected sensing diaphragm is supported by the respective substantial flat face of the center stop.

Abstract: A pressure measuring device wherein a housing (1) includes a pressure sensor (2) in a pressure chamber (4) and an electronic circuit (14) in a non-pressurized chamber (6). Borings (7) extend between pressure chamber (4) and non-pressurized chamber (6) and accommodate contacts that electrically connect pressure sensor (2) and electronic circuit (14). A pressure membrane (3) cooperates with housing (1) to further define pressure chamber (4) and isolate the device from the fluid system. Pressure chamber (4) is filled with a medium that transmits the system pressure and provides an output signal to electronic circuit (14).

Abstract: A pressure measuring device wherein a housing (1) includes a pressure sensor (2) in a pressure chamber (4) and an electronic circuit (14) in a non-pressurized chamber (6). Borings (7) extend between pressure chamber (4) and non-pressurized chamber (6) and accommodate contacts that electrically connect pressure sensor (2) and electronic circuit (14). A pressure membrane (3) cooperates with housing (1) to further define pressure chamber (4) and isolate the device from the fluid system. Pressure chamber (4) is filled with a medium that transmits the system pressure to pressure sensor (2). Pressure sensor (2) measures the pressure and provides an output signal to electronic circuit (14).

Abstract: A dual differential pressure/static pressure unit including a housing and three approximately parallel diaphragms sealed therewith forming low and high pressure compartments. Incompressible fluid then fills the respective spaces between the center diaphragm and that on each side thereof. Differential pressure/static pressure sensors are then provided. The housing is provided with passageways to conduct each of said fluids to the respective high and low pressure sides of said sensors.

Abstract: The head for the hydrostatic detection of a liquid level includes a main enclosure which is divided by a membrane into two chambers, one of which communicates with a supply of air under pressure, while the other is joined to a probe that is immersed deeply into the liquid. That connection is made, in this case, by the intermediary of an auxiliary enclosure that also contains a primary chamber that communicates with the inlet of the air under pressure, and a secondary chamber which is separated from the primary chamber by a membrane. That membrane forms one piece with a valve mounted between the chamber and a small connecting conduit connected with a probe, which prevents any ill-timed rise of the liquid inside the device, in the case of the disappearance of the compressed-air supply, and which makes it possible, at the same time, to install the detector head above the tank.

Abstract: A semiconductor differential pressure transducer comprises a pair of pressure receiving chambers at both sides of a pressure receiving part, and a pair of compensating chambers and a pair of pressure measuring chambers which are placed in the pressure receiving part, and the pressure receiving chambers communicate with the pressure measuring chambers through the compensating chambers.

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 liquid filled pressure transducer which utilizes a self activating lip seal type valve to create a sealed cavity within the transducer to prevent the flow of liquid from behind the pressure diaphragm and thereby prevent distortion of the diaphragm under overload conditions. A mechanical stop prevents excess displacement of the sensor element.

Abstract: A pressure transducer assembly is disclosed for directly monitoring pressure in a fluid which flows through the assembly. The assembly includes a housing defining a chamber therewithin and having an inlet port and an outlet port in fluid-flow communication with the chamber. An electrically insulated body element is sealed within the chamber dividing the chamber into a first chamber and a second chamber. The first chamber is in fluid-flow communication with the inlet and outlet ports. The second chamber is separated from the first chamber by a fluid-tight seal such that any fluid present in the first chamber cannot enter the second chamber. A pressure transducer sensor is secured in the insulated body and exposed to the first chamber such that the sensor can determine the pressure in a fluid in the first chamber and convert the pressure into electric impulses. The sensor is separated from the fluid in the first chamber by an insulating medium across which fluid pressure can be determined.

Abstract: A pressure or pressure-difference measuring apparatus having a central pickup body and a pressure sensor device disposed within a measuring chamber, the subchambers of which are connected via connecting canals to antechambers formed between separating diaphragms and the central pickup body, is disclosed. The apparatus also has supplementary diaphragms resting against the pickup body and connected to the connecting canals through supplementary canals. A simplified mechanical design is accomplished by having single supplementary canals, each open to a connecting canal connected to a separating diaphragm, running to the supplementary diaphragm adjacent to the device's opposite separating diaphragm.

Abstract: A method and an apparatus which, when interposed or integrated into sensitive pressure analyzers of pressure and vacuum measuring engineering equipment, prevent the intrusion of corrosive or condensable gases, or vapors, into the inside of the analyzer, and hold back soiling (dust and dirt) particles contained in gaseous measuring media. The present development contemplates a low-frequency oscillating diaphragm body, disposed inside of a pressure, or vacuum sealed, duct housing, in such a way, that although it optically diametrically blocks the light tube connection, it allows static pressure compensation via one or several bypass boreholes; it forces, by its energy of motion, directly impinging soiling dust and dirt particles, and gas or vapor molecules, to change their original direction of motion. The present protection arrangement is utilizable not only in pressure ranges above atmospheric pressure, but also in vacuum up to an absolute pressure of <10 Pa.

Abstract: A semiconductor pressure transducer including a measuring diaphragm of semiconductor material for sensing pressure supported by a support member of the same material. An oxide layer and a thin glass layer are interposed between the measuring diaphragm and the support member.

Abstract: In a pressure or pressure difference measuring transducer comprising a diaphragm clamping housing which is held in a pressure housing by means of a ring shaped support element, and separating diaphragms which rest against suitably shaped formed beds of the pressure housing in the event of an overload, in order to obtain a comparatively compact design which can be produced at comparatively low cost, the support element is designed and connected to the pressure housing and the diaphragm clamping housing so that a connection of the pressure and the diaphragm clamping housing which is stiff in a direction parallel to the housing is produced.

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: A pressure receiving element for receiving an external pressure is attached to one end of a body and a temperature compensating diaphragm is attached to the other end of the body. A coupling shaft disposed in the body is fixed at both ends to the pressure receiving element and the diaphragm, respectively. A liquid is sealed in the body and means is provided for detecting displacement or force applied to the coupling shaft in accordance with a pressure received by the pressure receiving element. The diaphragm has corrugations of concentric circles and the crests of a plurality of them are made flat and one of the flat crests is fixed to the body. The effective area of the diaphragm inside of the flat crest that is fixed to the body is selected substantially to be equal to the effective area of the pressure receiving element.

Abstract: A knock detecting apparatus for detecting the occurrence of knocking in an internal combustion engine by detecting variations in the pressure of engine cooling water. A sealed double diaphragm structure is formed by a first diaphragm which is directly responsive to variations in the cooling water pressure and not resonant at the knock frequencies and a second diaphragm which is resonant at the knock frequencies. A noncompressible fluid is contained in the sealed double diaphragm structure between the two diaphragms. Pulsations of the second diaphragm, resonant at the knock frequencies, are detected by a magnetic device or a piezoelectric device operative to output an ac signal.

Abstract: A fluid pressure sensing device for a fluid-containing vessel, and a method of assembling said device, is disclosed. A metallic diaphragm is preferably laser-fused to one end of the sensing device to define the end surface thereof. The sensing device is preferably mounted and sealed with the wall of the vessel such that the diaphragm and such sealing engagement is substantially flush or coplanar with the inside surface of the wall. A passageway extending through the sensing device admits an indicator fluid to one side of the diaphragm for measuring the pressure of the fluid in the vessel. The passageway also includes an adjustable nozzle for pre-calibrating the sensing device.

Abstract: A pressure transducer for use in a direct blood pressure measuring system includes a domed portion which is connected to a line interposed in a patient's blood supply system. A sterile solution serves to interface the patient's blood system and the pressuring measuring apparatus. An asymmetrical configuration of the interior cavity in the domed portion of the transducer, which cavity is in the fluid flow path, as well as a convex surface formed on the top face of the cavity improve the reliability of the transducer by avoiding standing waves and bubbles in the fluid in the cavity. Flow lines intersecting the cavity are tapered to improve impedance matching with the cavity.

Abstract: An apparatus for protecting a pressure differential sensor from exceeding a maximum allowable pressure differential. The apparatus has a housing which has a low-pressure chamber and a high-pressure chamber. A pressure-sensitive member separates the high-pressure chamber and the low-pressure chamber from one another. A blocking member is provided for blocking the entrance of fluid into the high-pressure chamber in response to the pressure-sensitive member sensing an initial differential pressure between the high-pressure chamber and the low-pressure chamber which exceeds the maximum allowable differential pressure. There may also be provided equilibration structure for creating a hysteresis loop as to the magnitude of the pressure differential between the high-pressure chamber and the low-pressure chamber.

Abstract: A manometer is provided for metering samples of fluid flowing in devices wherein particle concentration in the fluid is being counted or measured. Such devices include particle counters for determining blood cell concentration in body fluid. The device includes low permeable stretchable diaphragms in the device connections for containing the mercury therein, and a slide valve in the vent connection to restrict the movement of the mercury during storage or shipment. The arrangement herein includes, also, a one-way valve downstream of the "stop" point to stop flow substantially immediately upon the cessation of the measurement interval to reduce unwanted airflow to the counting aperture. A start and stop arrangement in the mercury flow path for causing the leading edge of the mercury meniscus at the axis thereof to engage the electrode contacts includes simple wire tips extending into the mercury flow path to the axis thereof for engaging the axis of the mercury meniscus.