Abstract: A semiconductor pressure sensor utilizes single-crystal silicon piezoresistive gage elements dielectrically isolated by silicon oxide from other such elements, and utilizes an etched silicon substrate with an etch stop. P-type implants form p-type piezoresistive gage elements and form p+ interconnections to connect the sensor to external electrical devices. The diaphragm is made from epitaxially-grown single-crystal silicon. Passivation nitride can be used for additional dielectric isolation. One practice of the invention provides over-range cavity protection, and thus increased robustness, by forming an over-range stop for the diaphragm through localized oxygen ion implantation and etching.

Abstract: A selectively pressured housing apparatus comprising a body, a wall member, an aperture, and a mounting seat. The body has a chamber therein extending along a first axis, is open at a first axial end and a second axial end, and has a port extending along a second axis transverse to the first axis. The port communicates with the chamber. The wall member is inside of the body and extends transverse to the first axis and parallel to the second axis and divides the chamber into first and second compartments, axially spaced along the first axis. The port communicating with the chamber is in the second compartment. The aperture extends through the wall member and connects the first and second compartments. The mounting seat is on the wall member and extends circumferentially about the aperture for removably and replaceably seating an element with a selected pressure seal to the wall member.

Abstract: A method and apparatus providing an automated means for detecting unsoldered thru-hole connector leads is herein disclosed. This means consists of a thru-hole connection pad and a test pad positioned in close proximity to each lead of an electrical component. A thru-hole connection pad is formed about the periphery of each thru-hole. It serves to form a solder pad for securing the lead to the printed circuit board and establishes an electrical connection between the component and reverse sides of the printed circuit board. A test etch easily accessible by an automated testing device is positioned within close proximity of each thru-hole connection pad. As each lead is individually soldered to the printed circuit board, a solder bridge must also be formed across the thru-hole connection pad and the test etch thereby establishing an electrical connection between the lead and the test etch. This electrical connection is used by an automated testing device to detect any unsoldered leads.

Abstract: A semiconductor pressure sensor utilizes single-crystal silicon piezoresistive gage elements dielectrically isolated by silicon oxide from other such elements, and utilizes an etched silicon substrate. P-type implants form p-type piezoresistive gage elements and form p+ interconnections to connect the sensor to external electrical devices. The diaphragm is made from polysilicon and is deposited on top of the gage elements.

Abstract: An apparatus and method for automatically adjusting the control parameters of a self-tuning controller used to regulate a process having a measured process variable signal. Using the measured process variable signal, an error signal representing a closed-loop response of the process to an upset condition is generated. Local extrema of the error signal is measured and three successive amplitude values are selected to produce measured decay and overshoot characteristics of the error signal. The three successive amplitude values are selected such that the measured decay characteristic is greater than the overshoot characteristic. Based on the measured decay and overshoot characteristics at least one of the control parameters of the controller is automatically adjusted to improve the difference between one of the measured characteristics and a target characteristic.

Abstract: A pressure transmitter apparatus having a Unitary body portion, separate diaphragms and flange elements and disposed within the body, a first and second normally vertical pressure passage. The first and second pressure passageways communicate respectively between first and second pressure openings extending-normally horizontally through the body portion, and a transducer mounting element. The mounting element, coupled to the body portion and located above the pressure passageways, mounts a transducer that generates a differential pressure signal. One or a pair of diaphragm elements are configured to form first and second process diaphragms, closing first and second pressure openings. The flange element overlies the diaphragm element and is removably and replaceably secured to the body portion.

Abstract: A dual sensor vortex flow meter providing fluid connections for two sensors and containing isolation valves providing the further capability of separate valve control of the fluid communication to each of the dual sensors is herein disclosed. The vortex flow meter is mounted onto a flow meter body having an existing sensor cavity for housing a single sensor. The vortex flow meter is fitted into the existing sensor cavity by means of a dummy-cast sensor. On either side of the dummy sensor are apertures coupled to flow passages that transmit the alternating differential pressure fluctuations caused by the vortices from each side of the dummy sensor to the corresponding sides of each of the dual sensors. The dual sensor vortex flow meter may also include valves for controlling the process flow transmission to each of the sensors.

Abstract: A method and apparatus for increasing the resolution and accuracy of flow measurements made by vortex flowmeters through the use of an adaptive filter. A vortex sensor signal is conditioned by a bandpass filter whose corner frequencies are dynamically altered as a function of the measured frequency of the vortex sensor signal. When the change in frequency is relatively small, the filters' corner frequencies are set to track the frequency signal in accordance with a specified bandwidth thereby improving the signal-to-noise ratio. For large frequency changes, a new frequency signal is searched for thereby avoiding tracking erroneous noise signals. Furthermore, compensation for additional or missed vortex pulses is made thereby generating a more accurate vortex frequency measurement.

Abstract: An analog isolation circuit for providing electrical isolation between interrelated electrical circuitry contained within a vortex flowmeter. The circuit provides a low power and low cost solution to the problem of ground isolation presented in flowmeters utilizing grounded sensors which generate low frequency sinusoidal signals. A pair of clock-controlled analog switches couples the voltage difference between two successive samples of an analog signal across an isolation barrier. The operation of the switches at a low frequency rate and with a short sampling interval while utilizing a low magnetizing current preserves the magnitude of the input waveform while consuming approximately 1 mW of power.

Abstract: A method and apparatus for a robust process control system that utilizes a neural-network multivariable inner-loop PD controller cascaded with decoupled outer-loop controllers with integral action, the combination providing a multivariable nonlinear PID and feedforward controller. The inner-loop neural-network controller is trained to achieve optimal performance behavior when future process behavior repeats the training experience. The outer-loop controllers compensate for process changes, unmeasured disturbances, and modeling errors. In the first and second embodiments, the neural network is used as an inner-loop controller in a process control system having a constraint management scheme which prevents integral windup by controlling the action of the outer-loop controllers when limiting is detected in the associated manipulated-variable control path.

Abstract: A sensor for provides a measurement and information about the validity of the measurement. The sensor includes a transducer for generating a data signal related to the value of a variable and a transmitter for receiving the data signal and generating output signals. The transmitter generates a first output signal related to the value of the variable. The transmitter also generates a second output signal based on a dynamic uncertainty analysis of the first output signal.

Abstract: A method and apparatus for a robust process control system which utilizes a neural-network based multivariable inner-loop PD controller cascaded with decoupled outer-loop controllers with integral action, the combination providing a multivariable nonlinear PID and feedforward controller. The inner-loop PD controller employs a quasi-Newton iterative feedback loop structure whereby the manipulated variables are computed in an iterative fashion as a function of the difference between the inner loop setpoint and the predicted controlled variable as advanced by the optimum prediction time, in order to incorporate the downstream limiting effects on the non-limited control loops. The outer-loop controllers compensate for unmodeled process changes, unmeasured disturbances, and modeling errors by adjusting the inner-loop target values.

Abstract: The invention features a manifold that includes two cylindrical ports and a cavity that connects to a fluid line. The ports both have the same cross-sectional area, and the center axes of the ports are oriented at the same angle with respect to the axis of the cavity. The ports couple to the cavity through separate transition regions, one of the transition regions coupling to a region at one end of the cavity that is circular in cross-section, and the other transition region coupling to an aperture disposed in a wall of the cavity. Both transition regions provide continuous fluid flow paths to the respective ports.

Abstract: A monolithic flowtube for use with an electromagnetic flowmeter includes an inner portion formed of an improved purity dielectric material having a reduced number of mobile ions, a pair of electrodes adjacent the exterior surface of the inner portion and capacitively coupled thereto, and an outer layer of ceramic material adjacent the exterior surface of the inner conduit and electrodes. A method of manufacturing the flowtube includes the steps of forming a dielectric material into a substantially tubular conduit, depositing a conductive material, preferably a refractory metal, onto the exterior of the tubular conduit, forming an outer layer of ceramic material over the tubular conduit, and firing all components simultaneously in a reducing atmosphere to form a monolithic flowtube body.

Abstract: Multivariable adaptive feedforward control may be accomplished by detecting the beginning and ending of a process control disturbance response, characterizing the measured inputs and process output during the disturbance by moments, which comprise time-weighted integrals performed on the process result output and inputs when the disturbance is a measured disturbance, and relating the characterized inputs and process result output in known general transfer function model equations to generate transfer function parameters which are used to calculate the coefficients of feedforward additive or multiplicative compensators.

Abstract: A method of determining the degree z of a hyperbolic non-linear characteristic, of a process that is controlled by application of a manipulated variable signal thereto for varying a first characteristic thereof, and that generates a controlled variable signal representative of that first characteristic by applying a first pulse to the process by stepping the manipulated variable signal and observing the resultant maximum change in the controlled variable and then applying a second pulse to the process by stepping the manipulated variable in the opposite direction and observing the maximum change in the controlled variable, and using the ratio of the two maxima to determine the non-linear characteristic and make appropriate compensation in the controller.

Abstract: A modular pressure sensor has a pressure-sensing element, electrical terminals, interconnections, and a support substrate. The pressure-sensing element produces an electrical signal indicative of pressure at local contacts and the interconnections apply the signal to the electrical terminals. The electrical terminals are secured to the substrate and extend along a peripheral surface of the substrate. The modular pressure sensor can mount, with different orientations, to a header to form a pressure transducer.

Abstract: A method and apparatus for identifying an unknown gas by generating an infrared spectrum of the unknown gas using an infrared spectrophotometer that includes a circular variable interference filter, compressing the infrared spectrum of the unknown gas, and comparing the compressed infrared spectrum of the unknown gas to a library of compressed infrared spectra of reference compounds. After comparison, the compressed spectra that most closely match the unknown gas are decompressed and displayed. Because frequency characteristics of circular variable interference filters vary from filter to filter, information designating these frequency characteristics for the particular filter employed are used in generating the infrared spectrum of the unknown gas.

Abstract: An electromagnetic flowmeter with conventional orthogonal electrode and magnetic axes (x, y) intersecting the flowtube axis (z) has its electrodes constituted by two pairs (1, 2 and 3, 4) of electrodes mounted in insulating tubing (5) on each side of the flow passage through the tubing. Four conductors extend respectively from the four electrodes to enable the potential difference between the two electrodes on each side due to an axial component on each side of eddy current electric field in the liquid to be determined for self-calibration purposes in compensating automatically for any extraneous change in the magnetic field and the average potential of each pair of electrodes can also be determined to derive the velocity of flow of the liquid. One of the two pairs of electrodes can be replaced by a single electrode.

Abstract: A sensor for use in a vortex flow meter which is capable of measuring various physical characteristics of a flow in a single process penetration from a common source. A shedder bar in the vortex meter generates alternating vortices. The sensor is located in the shedder bar within the stream of the fluid flow. The shedder bar serves as a composite vortex-generating plate and sensing unit. The shedder bar is structured such that it is either removable from the flow pipe for calibration, replacement, cleaning and the like or is permanently welded into the flow pipe with smooth or rigid contact surfaces. The sensor comprises one or more sensing diaphragms containing piezoresistor elements arranged in a Wheatstone bridge configuration. The sensor produces electric signals indicative of flow velocity, fluid pressure, and temperature. These signals are transmitted to a processing element which computes additional flow parameters.