Abstract: In a digital transducer, the output of a piezoelectric transducer bridge is coupled to the input of a comparator whose output switches between two predetermined states. A series of digital values is generated in response to the state of the comparator output and is fed back to balance the bridge. Stored digital values control the span of the transducer.

Abstract: A linear variable differential transformer (LVDT), includes a hollow bobbin with first and second ends, a ferromagnetic core adapted for linear movement within the bobbin, a primary coil wound around the exterior of the bobbin, and first and second secondary coils wound around the primary coil. The first and second secondary coils are wound from starting points at the first and second bobbin ends, respectively. The seconardy coils are then wound continuously and simultaneously toward the opposite bobbin ends, so that the two secondary coils cross over each other at a cross-over point approximately halfway between the bobbin ends. The second secondary coil thus overlaps the first secondary coil between the cross-over point and the first bobbin end, and the first secondary coil overlaps the second secondary coil between the cross-over point and the second bobbin end. Each of the secondary coils has a sufficient continuous length to overlay substantially the entire length of the primary coil.

Abstract: An apparatus for winding two coils simultaneously on a bobbin, such as winding the two secondary coils of a linear variable differential transformer (LVDT), has a chuck or the like holding a bobbin. The chuck is rotated by a first motor. First and second wire guides move linearly in directions opposite to one another along the axis of rotation of the bobbin, and guide two strands of wire onto the rotating bobbin. The wire guides arrive simultaneously at the longitudinal center of the bobbin where the two strands of wire cross one another. The two wire guides are driven by two lead screws which rotate at identical speeds but in opposite directions to one another. The lead screws are driven by a second motor. The speeds of rotation of both motors are controlled by a computer, whereby the pitch pattern of the windings is determined by a computer program.

Abstract: A pressure transducer of the type employing a pressure-responsive diaphragm (11) with silicon piezoresistive strain gauges epitaxially deposited thereon is provided with integral digital thermal compensation of span shift and zero shift. The strain gauges are connected in a bridge circuit (30), and a differential voltage across the bridge circuit is amplified by an instrumentation amplifier (46). A temperature sensitive resistor (36) is deposited on the pressure-responsive diaphragm. This resistor is connected in a bridge circuit (35) the output of which is connected to an analog-to-digital (A/D) converter (54) which generates a digital number corresponding to the measured temperature of the piezoresistive strain gauges. This digital number is used to address pre-programmed correction data stored in a programmable read only memory (PROM) (53). The numerical correction data from the PROM is converted by a digital-to-analog (D/A) converter (55) to an analog correction signal.

Abstract: A diaphragm-type pressure sensor employs a monocrystalline wafer as a pressure-responsive diaphragm. The wafer has a central active area surrounded by a first bonding area on one side and a second bonding area on the other side. The first bonding area is attached by a first layer of bonding material to a base, and the second bonding area is attached by a second layer of bonding material to a cap. The inside diameter of the first bonding layer is greater than the inside diameter of the second bonding layer by an amount of at least approximately six times the thickness of the diaphragm. This disparity between the respective inside diameters of the two bonding layers results in the relief of radially-directed tensile loading on the first bonding layer when a pressure to be measured is applied to the first side of the diaphragm. Consequently, the probability of a fracture occurring in this bonding layer is minimized.

Abstract: Silicon capacitive pressure sensors are produced by a batch-process method, comprising the steps of: (1) providing first and second wafers of conductive silicon; (2) oxidizing a surface of each wafer with a layer of silicon dioxide; (3) removing a predefined area of the silicon dioxide layer from a first one of the wafers, leaving an exposed surface of unoxidized silicon in the predefined area; (4) superimposing the second wafer onto the first wafer so that the silicon dioxide layer of the second wafer is in contact with the silicon dioxide layer of the first wafer; (5) fusing the two wafers together at their contacting silicon dioxide layers; (6) metallizing selected areas of the outer surfaces of the two wafers to form electrical contacts; and (7) cutting the wafers into individual pressure sensors.

Abstract: A pressure transducing device in the form of a beam includes a monolithic chip of silicon or similar material which is mechanically supported at and near its two opposed ends and unsupported in a flexible region between the two ends. The flexible, unsupported region is one of maximized sensitivity to stresses produced by deflection or flexing of the beam due to, e.g., a differential pressure applied across it. An integral, pressure-responsive diaphragm is formed in the supported area of the chip near one of its mechanically-supported ends. This area of the chip is relatively insensitive to stresses produced by beam flexing or deflection; rather, it responds to stresses produced by a pressure (e.g., a static pressure) applied directly to its surface. A first set of strain gauges is provided in the flexible chip region, and a second set on the surface of the integral diaphragm.

Abstract: An apparatus which utilizes solid state piezoresistive strain sensing means to measure the static pressure as well as the differential pressure across a primary element, such as an orifice plate, venturi tube, nozzle or wedge.

Abstract: An apparatus which utilizes solid state piezoresistive strain sensing means to measure the static pressure as well as the differential pressure across a primary element, such as an orifice plate, venturi tube, nozzle or wedge.

Abstract: In a differential pressure transducer, of the type having a cantilever beam mechanically linked to a pressure-sensitive diaphragm, and piezoelectric strain gauges diffused into or bonded onto the beam, the beam has a relatively high compliance as compared with the diaphragm to facilitate operation in low pressure ranges and to increase the overall operating range of the unit. In addition, the beam is constructed so that the total bending energy is transmitted to the area of the strain gauges so as to achieve near-perfect operating efficiencies.