Abstract: A single pressure sensing capsule has a reference pressure ported to the rear side of a silicon sensing die. The front side of the silicon sensing die receives a main pressure at another port. The silicon sensing die contains a full Wheatstone bridge on one of the surfaces and within the active area designated as the diaphragm area. Thus, the difference of the main and reference pressure results in the sensor providing an output equivalent to the differential pressure, namely the main pressure minus the reference pressure which is the stress induced in a sensing diaphragm. In any event, the reference pressure or main pressure may be derived from a pump pressure which is being monitored. The pump pressure output is subjected to a pump ripple or a sinusoidally varying pressure. In order to compensate for pump ripple, one employs a coiled tube. The tube length is selected to suppress the pump ripple as applied to the sensor die.

Abstract: A pressure switch employs a Wheatstone bridge incorporating piezoresistive elements. The output of the bridge is monitored by a control circuit which produces a first control signal when a high pressure is achieved and produces a second control signal when a low pressure is achieved. The output of the control circuit is coupled to the gate electrode of a high current MOSFET device. The drain electrode of the MOSFET is coupled to one terminal of the motor where the other terminal of the motor is coupled to an operating potential. The source electrode of the MOSFET is coupled to ground. When the monitored pressure reaches a high threshold the MOSFET turns off as biased by the control circuit which in turn disables the motor. If the pressure drops, the control circuit detects this and produces the control signal, which activates the motor through the MOSFET.

Abstract: A pressure restrictor for use with a pressure sensing element comprising a cylindrical member of a given diameter and length having a plurality of apertures directed from a first end to a second end is disclosed. A pressure restrictor housing holds and positions the cylindrical member in close proximity to the pressure sensing element at the second end by clamping the pressure restrictor between the housing and element. The apertures provided in the pressure restrictor are the sole path for application of pressure to the sensing element. The sensing element is a double diaphragm silicon sensor where one diaphragm is exposed to pressure and the other diaphragm is not exposed to pressure. Each diaphragm has located thereon a half-bridge wherein both half bridges are connected to provide a full bridge. The full bridge provides an output strictly proportional to pressure.

Abstract: A sensor is described, which basically consists of a leadless high sensitivity differential transducer chip which responds to both static and dynamic pressure. Located on the transducer are two sensors. One sensor has a thicker diaphragm and responds to both static and dynamic pressure to produce an output indicative of essentially static pressure, the static pressure being of a much higher magnitude than dynamic pressure. The other sensor has a thinner diaphragm and has one side or surface responsive to both static and dynamic pressure. The other side of the differential sensor or transducer structure has a long serpentine reference tube coupled to the underneath of the diaphragm. The tube only allows static pressure to be applied on the underside of the diaphragm and because of the natural resonance frequency of the tube, the dynamic pressure is suppressed and does not, in any manner, interface with the sensor or transducer having a thinned diaphragm.

Abstract: A high pressure transducer has an H shaped cross-section with a center arm of the H having a top and bottom surface with the top surface of the H accommodating four strain gauges. Two strain gauges are located at the center of the top portion of the center arm of the H and are positive strain gauges, while two strain gauges are located near the periphery of the center arm of the gauge. The bottom surface of the center arm of the gauge has an active area of a smaller diameter than the circular diameter of the center arm portion of the transducer. The smaller active area is surrounded by a thicker stepped area which surrounds an active area on the pressure side of the H shaped member.

Abstract: A pressure header assembly has a closed front and back surface. The back surface has an aperture for accommodating a separate dual die pressure header. The dual die pressure header has an absolute and differential pressure sensor positioned thereon. A differential pressure port is located on a side surface of the pressure header assembly and is directed to a bore in the pressure header assembly. The bore contains an elongated tube which is positioned in the pressure header assembly and locked in place by means of a crush nut and locking nut assembly. One end of the tube is coupled to the differential pressure port, while the other end of the tube accommodates a differential pressure tube which is bent in an arcuate position and directed to the underside of the sensor of the differential sensor assembly mounted in the dual die pressure header.

Abstract: A system for sensing at least one physical characteristic associated with an engine including a turbine having a plurality of blades turning inside a casing, the system including: a pressure sensor coupled substantially adjacent to the casing and including at least one output; a port in the turbine casing for communicating a pressure indicative of a clearance between the blades and casing to the pressure sensor; a cooling cavity substantially surrounding the pressure sensor; and, an inlet for receiving fluid from the engine and feeding the fluid to the cooling cavity to cool the pressure sensor; wherein, the pressure sensor output is indicative of the clearance between the blades and casing.

Abstract: A circuit produces an output that is proportional to the molar density of gas in a chamber. The circuit employs an operational amplifier which measures the temperature using a RTD or other element that changes resistance with temperature. The RTD is placed such that it produces a decreasing current draw at the inverting input of the operational amplifier as the temperature increases. This decreasing current draw in turn produces a decreasing voltage at the output of the operational amplifier. By changing the ratio of resistors connected to the non-inverting terminal of the operational amplifier one changes the offset of the output voltage. By changing the feedback resistor connected from the output of the operational amplifier to the inverting terminal and connecting the output of the inverting terminal to a voltage divider including the RTD device, one can change the gain with temperature.

Abstract: A high pressure transducer has a metal housing with a main inlet high pressure port at one end and a reference pressure port at the other end. The ports communicate with a central hollow of the housing. Positioned in the hollow and communicating with the main inlet port is a first header welded to the housing and containing a first sensor device. Also positioned in the hollow and communicating with the reference pressure port is a second header also welded to the housing and having a second sensor device. There is another high pressure port on the housing and located between the inlet and reference ports to receive a main inlet high pressure as applied to said main inlet port and when a reference pressure is applied to said reference port. The applied pressures cause the first header weld to experience zero stress due to the application of the same main pressure to both the main inlet port and another pressure port.

Abstract: A high temperature pressure transducer is fabricated from silicon carbide. A wafer of silicon carbide has reduced or active areas which act as deflecting diaphragms. Positioned on the reduced or active area is a silicon carbide sensor. The sensor is secured to the silicon carbide wafer by a glass bond. The pressure transducer is fabricated by first epitaxially growing a layer of highly N-doped 3C silicon carbide on a first silicon wafer or substrate. A second wafer of silicon carbide is selected to be a carrier wafer. The carrier wafer is etched preferentially to produce the deflecting members or reduced areas which serve as diaphragms. The 3C material on the silicon slice is patterned appropriately to provide a series of individual piezoresistors which then may be interconnected to form a Wheatstone bridge.

Abstract: A joystick apparatus employs a hermetically sealed load cell having strain gauges placed on flexible beams formed on the load cell. All of the strain gauges are on the same surface of the load cell and therefore wiring is performed on a single side of the load cell. The strain gauges are enclosed in hermetically sealed cavity. The sensing diaphragm consists of a concentric thick inner and outer section joined by thinner diametrically opposed beam elements. The thin beam elements are compliant members which can deflect. Each beam includes strain gauges or sensor elements and the load cell is coupled to a joystick which when moved causes the beams to deflect to cause the sensor elements to produce an electrical output proportional to the force and direction of the joystick. The sensor can yield an output proportional to any angle over the 360° movement of the joystick to provide outputs proportional to the X and Y positions of said joystick.

Abstract: An interface for facilitating facsimile transmission via a wireless communications device operatively connected to a wireless communications network, including: a modem suitable for being communicatively coupled to a facsimile machine; a controller coupled to the modem; and, a memory operatively coupled to the controller. The interface includes code to cause the modem to transmit a retrain request to the facsimile machine upon expiration of a given temporal period. The interface includes a circuit for selectively generating a ring signal corresponding to a plain old telephone service ring signal. The interface includes a circuit for selectively generating a hold signal corresponding to a plain old telephone service hold signal. And, the circuit includes code to cause the modem to transmit data indicative of white lines to the facsimile machine upon expiration of a given temporal period.

Abstract: A pressure probe includes a longitudinal tubular housing symmetrically disposed about a central axis and having an ultra miniature conical front end and an opened back end. A plurality of aperture ports having an opening are disposed about the front end. A plurality of ultra small leadless transducers has a central active deflecting area in a semiconductor substrate, and a layer of oxide on a bottom surface. At least one sensor network is disposed within the active area on the oxide layer. A glass contact wafer is bonded to the non-deflecting portion of sensing network and has a number of apertures surrounding the active area suitable for interconnection with header. A header encloses each transducer and is of a shape and size to be positioned in an associated aperture port of the probe housing. At least one lead is coupled to a header pin extending from bottom of the aperture and directed through the bottom opening into the hollow of the probe housing.

Abstract: A pressure transducer for measuring pressures in high temperature environments employs a tube which is terminated at one end by an acoustic micro-filter. The acoustic filter or micro-filter has a plurality of apertures extending from one end to the other end, each aperture is of a small diameter as compared to the diameter of the transducer and the damper operates to absorb acoustic waves impinging on it with limited or no reflection. Mounted to the tube is a pressure transducer with a diaphragm flush with the inner wall of the tube. The tube is mounted in an aperture in a casing of a gas turbine operating at a high temperature. The hot gases propagate through the tube where the pressure of the gases are measured by the transducer coupled to the tube and where the acoustic filter operates to absorb acoustic waves impinging on it with little or no reflection, therefore enabling the pressure transducer to be mainly responsive to high frequency waves associated with the gas turbine operation.

Abstract: A high temperature pressure capacitor is fabricated utilizing two high temperature substrate wafers. The substrates may be silicon carbide (SiC) or aluminum nitride (AIN). The first substrate has a metal conductive plate positioned on a top surface thereof. The top surface and plate are covered with a dielectric layer. The second substrate has a plate accommodating recess on the top surface thereof. Deposited in the recess is a second conductive plate. The first and second wafers are bonded together via the dielectric layer where the first and second plates face each other. Upon application of a force to the first wafer the diaphragm portion of the first wafer deflects causing the first plate to move and thereby varying capacitance. An inductor may be fabricated on a bottom surface of the second wafer to provide an LC circuit whose resonant frequency varies as a function of capacitance and therefore as a function of pressure.