Abstract: A microminiature resonant hollow beam sensor is manufactured by micromachining and microfabrication techniques. Specifically, a sensor is formed by etching troughs in a pair of silicon substrates, joining the substrates face-to-face, and etching away unwanted material to free the resonant hollow beam sensors.

Abstract: An apparatus for determining the heating value of a fuel gas stream of variable composition utilizes a housing of high thermal conductivity defining a small volume combustion chamber, and filled with a bed of highly thermally conductive particles surrounding an electrical-resistance heater. The heater maintains the internal temperature of the chamber above the combustion point of the fuel gas, to totally combust the enclosed sample. The bed of particles transmits the heating effects of the combustion to the housing. A temperature sensor attached to the housing communicates with a feedback controller which acts to maintain the housing temperature constant, by appropriately adjusting the electrical energy supplied to the heater. Means are provided to correlate changes in the electrical energy to the heating content of the fuel sample.

Abstract: A differential-pressure transmitter having a range diaphragm and a slack diaphragm to receive process pressures and to apply such pressures to an interior sealed chamber containing a fill-liquid. A vertically-oriented tube containing liquid communicating with the instrument fill-liquid contains a ball movable by gravity down through the liquid to create a reference-pressure pulse directed to the range diaphragm to provide for checking instrument performance. A relatively large weight is suspended from the ball to increase the effect of gravity on the ball, so as to increase the magnitude of the reference-pressure pulse. A flexible seal-and-pivot connection is provided at the top of the tube to permit substantial inclinations of the instrument relative to vertical without interference with the wall of the tube. The additional weight is in one embodiment divided into vertically-separable segments to provide for successive bottoming of the segments as the weight descends, to provide a stepped pressure pulse.

Abstract: A pattern-recognizing, self-tuning controller is provided for controlling a process wherein measured characteristics including at least one peak of an error signal, derived from the differences occurring over time between the values of a process controlled variable and a desired set-point level for that variable, are used for identifying the behavior pattern of the error signal so that an operating parameter of the controller can be changed as required to minimize process recovery time whenever the process is subsequently disturbed or an abrupt change is made to the set-point level at some later time. The preferred embodiment of the device is in the form of a proportional-integral-derivative (PID) controller in which the PID coefficients are calculated in accordance with prescribed relationships that are based on damping, overshoot and time period characteristics of the error signal.

Abstract: Drying material such as lumber by controlling the difference between inlet drying air dry bulb temperature and outlet drying air dry bulb temperature while maintaining wet bulb temperature constant, so that drying is characterized by a constant rate of evaporation.

Abstract: An apparatus usable in process control applications for detecting the position of a movable element in a sensor wherein first and second beams of light, each having different wavelengths and each preferably being alternately generated with respect to one another by a light source, are transmitted to a filter by means of an optical fiber cable connected between the light source and filter. The filter and the movable element cooperate for modulating the intensity of the first beam in accordance with the position of the movable element and thereby transforming that first beam into a measurement beam which appears at an output stage of the filter. The filter also transmits the second beam therethrough unaffected by the movable element and produces a reference beam appearing at the output stage. A first optical detector coupled to the light source the respective intensities of the two light beams being transmitted towards the filter.

Abstract: An element interacting with a stream of a fluid moving through a pipe generates periodic sub-flows at a rate that varies in accordance with changes in the velocity of the moving fluid. The generation of sub-flows also modulates the electrical charges contained in and moving with the fluid thus permitting a detector which is responsive to the energy being radiated by the modulated charges to produce a sensor signal having a frequency corresponding to the generating rate of the periodically produced sub-flows. In one preferred embodiment, the element is a vortex-shedding body and the sub-flows are vortices being shed therefrom. Electrical circuitry which receives the sensor signal converts it into a flow signal representative of the velocity of the moving fluid.

Abstract: A nonporous composite electrode, particularly suitable for use in electromagnetic flowmeters, includes a non-metallic, electrically conductive element consisting of a fused mass of polymeric material, such as perfluoroalkoxy (pfa) fluoropolymer, and carbon fibers. The electrode is fabricated by stacking alternating layers of polymeric film and carbon fiber paper, subjecting the assembly to sufficient heat and pressure to intermix the two components and bond them into a coherent mass, and fusing the resultant composite material onto a mounting pin. Using a polymeric material compatible with the polymeric liner of an electromagnetic flowtube allows the finished electrode to be fused into the liner, again by application of heat and pressure, so as to achieve a seamless interface. This configuration virtually eliminates process fluid leaks around the electrode, while the electrode structure itself exhibits exceptional high temperature stability and corrosion resistance.

Abstract: A method and apparatus for calibrating a liquid level measurement system of the type having capacitive sensors, by simulating the electrical effects of sensors in an empty condition and their interconnecting cables, at a time when the sensors are full or partially filled. By a sequential balancing technique, using a conventional bridge circuit, a precision, highly stable variable impedance device is adjusted to individually simulate the effects of each sensor and cable combination with the sensor in an empty condition. The settings of the variable impedance device are recorded, and at a later time when the sensors are no longer empty, these settings are reproduced, so as to recreate the electrical effects of each sensor cable combination one at a time. The individual effects are separately transferred into a network having a plurality of variable impedance channels, until each channel simulates the effects of a corresponding sensor and cable.

Abstract: A process control system includes redundant digital controllers and a plurality of input/output (I/O) modules for interfacing with remote field sensors and actuators. Bi-directional communication between controllers and I/O modules is achieved by a parallel-wired, process I/O bus. Failures within the system, including the bus structure itself, that continually keep the bus active (i.e., in a low state) are isolated by a combination of software diagnostic routines for performing bus checkout and a unique quick disconnect feature that readily isolates the fault condition first between the I/O module nest area and the controllers, then, if necessary, to individual I/O modules. During fault isolation procedures, individual I/O modules may be disconnected from the bus while the values of field signals are simultaneously maintained to provide minimum process upset.

Abstract: A vortex-shedding mass flowmeter which includes a shedding body mounted in a pipe containing a flowing fluid, a first detecting element that responds to the vortices generated when the fluid flows past a surface of the shedding body for producing a velocity signal proportional to the flow rate of the fluid, a second detecting element for sensing in a measuring plane that includes the surface of the shedding body where vortices are generated a moving fluid characteristic dependent on the product of fluid density and the square of the fluid flow rate, and electronic circuitry coupled to the outputs of the first and second detecting elements for producing therefrom a mass flow rate signal. In one preferred embodiment, the second detecting element is a pitot-type head device which senses a pressure differential between static and dynamic pressures existing at two locations on the measuring plane.

Abstract: A small line-size vortex meter comprising a small-diameter flow tube cast with an integral vortex-shedding bar and an external sensor housing. The outer surface of the housing is formed with an approximately circular recess extending towards the flow tube and communicating with the interior of the tube through side-by-side impulse ports located adjacent one end of the vortex-shedding bar. Inserted into the central region of the recess is a sensor body having diaphragms on opposite sides to respond to vortex pressure fluctuations transmitted through the impulse ports to chambers along the sides of the sensor body. The sensor body comprises an oil-filled capsule with the diaphragms serving to transmit the pressure fluctuations to a piezo-electric sensor element which produces corresponding electrical signals.

Abstract: An instrumentation system for use in measuring and processing industrial process variables, such as flow, pressure, or temperature, includes a resonant element sensor whose resonant frequency varies in accordance with changes in the desired process variable communicating through an optical fiber link to a distant control room. The sensor is activated into resonant physical motion by light energy from a source in the control room, while the motion of the wire is sensed optically and retransmitted to the control room to produce an output signal whose frequency is equal to that of the resonating element. A feedback network maintains the sensor in resonance by synchronizing the delivery of light energy to the motion of the resonant element. The powering and sensing aspect may be performed by individual fiber optic cables or alternatively this function may be combined by utilizing a single fiber optic strand.

Abstract: A target flowmeter includes a target body with an aperture through its impact surface, to equalize the forces generated on the target under both laminar and turbulent fluid flow conditions, as well as in the transition region therebetween. In a particular embodiment, the target body has an annular shape and is centered about the pipe center line, the size of the aperture being such that the target is acted upon by only those portions of the laminar and turbulent flow profiles having substantially similar shapes. Since the annular body is unaffected by the high velocity peak of the parabolic laminar profile, the force versus velocity relationship in the laminar flow range is approximately the same as in the turbulent flow range. This results in a more consistently accurate flow velocity measurement across the two flow regimes. Specific dimensional relationships between the size of the aperture and that of the pipe serve to optimize these results.

Abstract: A magnetic flowmeter of the capacitively-coupled type includes low-input impedance detection circuitry which responds to a flow induced current signal that is related to the voltage induced at the electrodes by the intersection of the flowing fluid and a time varying magnetic field. An on-line measure of the electrode capacitance that is non-interactive with the flow induced current signal is accomplished by creating a voltage difference between the process fluid and the electrodes which causes a capacitance-related current to flow from the electrodes proportional to the value of the electrode capacitance as well as the rate of change of the magnetic field. In one embodiment the primary element and the detection circuitry are referenced to a different potential than that of the process fluid and the adjacent piping of the flow system.

Abstract: A gas chromatographic column comprising synthetic fused silica tubing irradiated in its raw state with gamma radiation of pre-selected dosage and dosage rate. The column further comprises a stationary phase coating of cyano-silicone immobilized and stabilized by cross-linking in situ by means of further irradiation by gamma radiation.

Abstract: An apparatus for determining the proportion of water within a mixture of water and a water-miscible solvent includes means for increasing the electrical conductivity of the mixture in proportion to the amount of water contained therein. In a particular embodiment this is done by passing a component stream of the sample through a replenishable bed of a salt, which salt is easily soluble in water but is relatively insoluble in the solvent. The dissolving of the salt introduces an appreciable number of conductive ions into the mixture, thereby enhancing its overall conductivity. A conventional detecting scheme measures the enhanced conductivity of the mixture, and means is provided for correlating this conductivity measurement to the proportion of water within the mixture.

Abstract: Control of multiple distillation columns for producing anhydrous alcohol suitable for blending with gasoline to produce gasohol. The distillation process involves production of a first-stage distillate containing a predetermined amount of water, followed by azeotropic distillation in the presence of a hydrocarbon entrainer to strip the distillate of its water content, leaving anhydrous alcohol as a bottom product. Tight controls are present during first-stage distillate production to hold its proof at an optimum value derived at through material balance calculations to minimize energy consumption for the overall system. Control over the dehydrating stage is accomplished by a combination of ratio control to regulate and maintain the proper proportion of the entrainer and temperature control to regulate within the column the actual inventory of entrainer.

Abstract: A gas chromatograph for measuring the amounts of selected sample gas components such as oxygen and carbon monoxide. The system comprises a high-temperature (600.degree. C.) zirconia cell detector supplied on one side with a continuous stream of oxygen flowing at a constant rate. A voltage source connected to the zirconia cell transports all of this oxygen to the other side of the cell, resulting in a constant background cell current. Sample components from the chromatographic column are injected sequentially into the oxygen stream. When oxygen is injected the cell current increases due to the increase in total oxygen available for transport through the cell. When carbon monoxide is injected, it is fully combusted with the oxygen, and the current correspondingly decreases due to reduction of the oxygen available for transport. The deviation in cell current with reference to the background current is integrated for each component to produce output signals indicating the amount of the component.

Abstract: An interferometer mirror drive system compensates for velocity and tilt errors induced by ambient vibration, as well as providing long-term automatic alignment of the mirrors. A uniquely configured .lambda./8-thick step on the fixed mirror of the interferometer introduces a 90-degree phase shift in one of two reference light beams, to produce quadrature signals which characterize the relative motion between the fixed and the driven mirrors. An electronic circuit extracts velocity and tilt data from the quadrature signals and develops error signals indicative of deviations from the desired coordinates of the moving mirror. The error signals are used to generate a set of control signals which in turn are supplied to an arrangement of drive coils attached to the moving mirror, to restore the mirror to the desired coordinates.