Abstract: A process control instrument, in which the resonant frequency of a vibrating string varies in accordance with changes in a process parameter being monitored, employs a pneumatic drive system to induce the string into oscillation. Pressurized gas is discharged through a port, such as a jet nozzle, which is disposed to allow the gas to impinge on the outer surface of the string. Variations in the alignment between the gas discharge port and the string permits different modes of vibration, one of which is particularly suitable for process measurement purposes. In a particular embodiment of the apparatus, an optical sensor detects the frequency of vibrations, resulting in an intrinsically safe instrument for use in explosive environments.

Abstract: A resonant wire instrument for producing a measurement signal, which is derived from the resonant frequency of a vibratable wire tensioned in accordance with the magnitude of a physical variable being measured, wherein a force impulse produced mechanically by an apparatus is applied to displace laterally one end of the vibratable wire so as to excite the wire into resonant motion. In one embodiment, the one end is rigidly attached to a housing and a piston applies a transverse force impulse to that end by momentarily striking the housing. In another embodiment, the one end is connected to a piezoelectric crystal which responds to a short-duration electric field to displace momentarily that end.

Abstract: A heating device, usable in an oven for heating chromatographic equipment, includes an intake for passing an air flow produced by an air supply connected thereto into a cavity formed inside of a tubular member. A heating element, preferably located within that cavity, heats the air flow to an elevated temperature as well as the walls of the tubular member. A heater housing having an enclosed volume contains the tubular member. The heated air flow passes from the cavity into the enclosed volume where it is distributed along both the interior surfaces that define the enclosed volume and the outside of the walls of the tubular member. The interior surfaces are thereby heated while the heated air flow receives further heat from the heated cavity walls. A manifold including an elongated portion having a plurality of apertures formed therethrough with integral nozzles is connected to the heater housing for receiving therefrom the heated air flow.

Abstract: An ion-sensitive electrode, usable for measuring the activity or concentration of a predetermined ion in a fluid stream of an industrial process, includes a vessel partially filled with an electrolyte and fabricated with one wall portion thereof comprising a rigid, porous fritted back-up element and a relatively thin, ion-sensitive, non-porous membrane. Being preferably made of the same ion-sensitive material as the membrane, the back-up element is produced using a sintering process which results in a porous solid having maze-like passages extending randomly therethrough in all directions. One surface of the back-up element is fused to and supports a thin layer of ion-sensitive material that has been applied to the back-up element, heated to its molten working temperature and then cooled to form the non-porous membrane. Located within the vessel, the back-up element also serves to transport the electrolyte through its passages for wetting the interior surface of the thin membrane fused to the back-up element.

Abstract: A body for improved shedding of vortices within a flowing fluid has a very short downstream length, e.g. 1/8 inch, yet is capable of excellent flow metering performance. The body includes an upstream elongate thin plate spanning the inner diameter of a conduit, and one or more sections projecting downstream of the plate. Generally, these sections are in the form of cylindrical rods having circular, rectangular, or oval cross-sections, with their longitudinal axes parallel to the longitudinal axis of the plate. Although these sections may be separated from the plate, in certain embodiments they are rigidly attached to the downstream side thereof. By simultaneously maintaining the ratio of the width (i.e., transverse to the flow direction) of the thin plate to the overall width of the downstream sections within the range from 1.0 to 2.2, and the ratio of the width of the thin plate to the diameter of the conduit within the range from 0.1 to 0.

Abstract: A compact ribbon-indicator and chart-recorder instrument for use in process control systems adapted to indicate and simultaneously record the values of up to three independent process variables. The motive power for each pen/indicator drive system is supplied from a corresponding relatively high-speed stepping motor. Each such motor is servo-controlled by a feedback circuit including a potentiometer coupled to the pen drive cable for developing a d-c feedback signal to be compared with the d-c measurement signal. The system is arranged to actuate the motor immediately upon development of a deviation signal outside of a fixed dead-band, but the extent of initial motor movement is limited to a pre-set small amount (preferably one step). If the deviation signal still is outside of the dead-band after a predetermined period of time, a clock pulse oscillator is turned on to actuate the motor at a relatively rapid rate until the deviation signal returns to the dead-band.

Abstract: A pressure transmitter is provided for producing a voltage signal representative of the magnitude of pressure being applied to a diaphragm of the transmitter, wherein a network including strain-sensitive resistors that are formed in the diaphragm is coupled to the output of a constant-current power supply for producing the voltage signal in response to the strain generated by the applied pressure in the diaphragm and a feedback circuit operates in a non-linear manner for generating a control signal in response to a temperature signal produced by the network. The power supply coupled to receive the control signal is responsive thereto for changing the current supplied to the network so that compensation is thereby provided for errors in the pressure measurement caused by changes in the temperature of the network resistors.

Abstract: Analysis of hydrocarbon mixtures to determine desired characteristics, particularly a determination of octane number of gasolines, undergoing partial oxidation/cool flame reactions. Pre-analysis performed on a target fuel sample of known composition and octane number is utilized to arrive at an optimum point of the reaction, a point believed to represent a condition where a maximum of the fuel is oxidized during the reaction. In the preferred embodiment disclosed, the optimum point is the reactor block temperature that generates a maximum peak temperature rise of the cool flame reaction of the target fuel. This optimum reactor temperature is utilized in further analyses of other known samples to develop a matrix of peak temperature rise versus time to reach peak coordinates. Any unknown fuel sample whose peak amplitude/time coordinate is within the matrix is compared with matrix values to determine its octane number as well as an indication of its composition.

Abstract: A self-cleaning optical device, suitable for use in dirty process environments has a composite, multi-layered structure. A protective outer layer, exposed to the process environment, is a transparent plastic film which is resistant to the adhesion of contaminants to its surface. A light-interactive layer, either light-transmissive or light-reflective depending on the intended function of the optical device, is disposed beneath the protective plastic film layer. A semi-rigid plastic material forms a support layer to give the device structural integrity. The optical device is vibrated to shake loose collected particles from the protective plastic film. The vibrational motion is generated either externally or by excitation of piezoelectric materials incorporated into the device construction.

Abstract: A non-imaging optical energy transfer system includes a tapered light pipe and associated field lens as its central energy transfer mechanism. The light pipe/lens combination is located between two separate sections of the system which individually have the same throughput or etendue but otherwise differ in f/#, beam focus, and pupil sizes. The transfer system is disclosed used in combination with a circular variable filter-absorption cell infrared spectrometer and an internal reflection spectrometer, employing a multiple internal reflection crystal.

Abstract: A vortex-sensing fluid flowmeter has a freely rotatable vortex-shedding body suspended in a section of conduit through which a fluid stream passes, the body being oriented generally transverse to the direction of fluid flow. The body has an integrally formed upstream-facing portion adapted to shed a series of vortices within the fluid, which vortices alternately influence opposite lateral faces of the body, tending to produce a periodic rotation of the body about a firmly attached rotational shaft. The shaft is rotatably mounted to the conduit and passes at one end through the wall of the conduit to the exterior thereof. A sleeve-like tube surrounds the shaft and is fastened tightly at its bottom end to the shaft and at its top end to the conduit wall to provide a fluid-tight seal around the shaft. The tube is sufficiently flexible and pliable to exert negligible restraining force against the rotation of the shaft.

Abstract: A turbine flowmeter includes a rotor within a narrow-profile housing, the rotor having an axis of rotation aligned perpendicularly to the direction of fluid flow. The rotor employs a pair of oppositely directed, semi-cylindrical rotor elements disposed on either side of the axis of rotation, arranged in a generally rectangular configuration. Each element has a high drag front surface and a low drag back surface, the elements being twisted with respect to the axis so that at least a portion of a high drag surface is presented continually to the incoming fluid stream. Due to the wide disparity in drag between the front and back surfaces, and this twisted orientation, there is produced a continuous unidirectional net driving torque acting on the rotor, to prevent the occurrence of a null point, despite counter-resistance offered by the fluid. Furthermore, the gradually curving rotor protrudes minimally beyond the housing, and is able to rotatively adapt itself to the narrow spacing between pipe flanges.

Abstract: An instrument for developing at a central control station a signal responsive to the value of a process condition occurring at a field measurement station remote from the central control station wherein a resonant device is used as the instrument basic sensor element. The resonant device which is located at the field station may be excited by either a voltage pulse or a continuous wave. In a particular aspect, the output measurement signal of the instrument is solely dependent upon the value of a desired measured variable, which is representative of a process condition, and is independent of other variables. The resonant device is coupled to excitation and detection circuitry located at the central control station and produces in the detection circuitry when excited with a pulse of energy first and second signals, one of which is dependent upon the desired measured variable and a second variable and the other dependent upon at least the second variable.

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 compact temperature-control unit for use with gas chromatographs. The unit includes a highly insulated enclosure with a removable lid having a gas chromatograph column wound on a thin-walled core fixedly positioned within the enclosure. Provisions are included for inserting a temperature-control module within the cavity formed by the core to achieve temperature control. A variety of different modules can be used to alter the desired control point.

Abstract: A process control system includes two digital controllers each capable of exercising direct digital control over the process. One of the controllers is selected to be on-control, the other serving as a backup. A separate data buffer memory connected to both controllers stores the most recent static and dynamic data base of the on-control controller which is transferred to the backup controller. In the event of failure or other loss of service, the backup automatically acquires control with an up-to-date data base resulting in a smooth transition. Provisions are also included to have the backup controller examine the health of the on-control unit before deciding whether or not to accept the data buffer contents thereby reducing the likelihood of corrupted data being fed to the backup.

Abstract: Chart recording apparatus for use with industrial instrumentation systems and the like, and comprising memory means to maintain a signal level for long time periods without drift. An input signal level is translated into the positioning of a pen, through the use of an actuator motor controlled by the input signal and a position feedback signal. A friction device is coupled to the pen to hold it in any given position, thereby to serve as a memory for the input signal level. The friction device comprises a thin vane-like element which is secured to the movable member and disposed in the air-gap of a permanent magnet. The air-gap also includes a mass of tiny magnetizable particles which, under the influence of the magnetic field, engage the surfaces of the vane-like element to develop a frictional restraining force.

Abstract: Instrument system including an electronic transmitter for a vibrating-wire differential-pressure sensor at a field location and connected by a two-wire line to a control room. The transmitter includes an oscillator to produce vibrations of the wire at its resonant frequency, and applies to the two-wire line a corresponding alternating voltage signal. The control room equipment converts this raw measurement data to an analog measurement signal. The control room equipment provides for adjustment of the zero and span of this signal, and for linearization with respect to the input differential pressure. The two-wire line carries a direct-current component the average value of which is automatically adjusted at the control room to match the scaled and linearized analog measurement signal. This line current passes through a meter at the transmitter to provide field service personnel with a visual indication of the value of the scaled and linearized measurement signal.

Abstract: An electro-pneumatic current-to-position transducer includes an electric motor having a permanent magnet for a stator and spring restrained coil pivotally suspended about the magnet for a rotor. An input current to the coil induces a mechanical rotation of the coil about the magnet which is proportional to the applied current. Fastened to the coil for rotary movement therewith is a flapper positioned to cover the nozzle of a pneumatic circuit. As current is applied to the coil, the flapper moves toward the nozzle thereby changing the back pressure in the pneumatic circuit. This change in pressure is amplified, then sensed by appropriate pressure-responsive devices and subsequently fed back to a control lever on which the nozzle is mounted, thereby repositioning the nozzle so as to maintain an essentially constant separation between the flapper and the nozzle.

Abstract: A force-measuring instrument of the vibrating-wire type wherein the mechanical components are located at the force-measuring location and the vibrating wire is coupled through a two-wire transmission line to electronic circuitry at a distant location. The electronic circuitry includes means to excite the vibrating wire and to produce a d-c measurement output signal corresponding to the frequency of vibrations. The electronic circuitry further includes function-generating means to establish a closely-linear relationship between the output current and the force applied to the wire. Means also are incorporated in the electronic circuitry for adjusting the zero and span of the instrument, and this can be done without interaction between the adjustments.