Abstract: An ultrasonic, echo-ranging instrument for measuring liquid level, the instrument including a transducer dispoed at a fixed position directly above the liquid surface. The transducer is excited to emit periodic pulses which are intercepted by the liquid surface as well as by a reference point a fixed distance from the transducer to produce both reference and liquid echo pulses that are returned to the transducer and detected thereby. The respective transit times of the reference echo and the liquid echo pulses are determined, and the ratio between these transit times is computed to provide an output representing the level of liquid. To ensure accurate readings, the reference echo and liquid echo pulses from the transducer are fed to a single automatic gain control circuit whose operation is time shared.

Abstract: A mass flowmeter of the Coriolis-type having a primary wherein fluid being metered is conducted through a flow tube in the form of a double loop whose loops are excited by a driver to vibrate in phase opposition at the resonance frequency of the tuning fork. Because fluid passing through the flow tube is subjected to Coriolis forces, the vibrating loops are caused to torsionally oscillate in accordance with the mass flow of the fluid. A pair of sensors mounted on the respective loops sensor signals which are applied to a differential amplifier in a signal recovery system forming the secondary of the meter to produce an output voltage that is a function of mass flow. This output voltage is applied to the input of a microcontroller coupled to an indicator providing a reading of mass flow. The meter is calibrated so that at the resonance frequency under normal operating conditions it produces a reading proportional to mass flow.

Abstract: A differential pressure transducer of the capacitive type responsive to fluid pressure. The transducer includes a cylindrical body having insulating sections at either end provided with a planar end face and a concave cavity surrounded by an annular rim. The cavities communicate with each other through an internal duct in the body and are filled with a dielectric fluid. Covering each cavity and sealed to the surrounding rim is a diaphragm provided with a movable electrode which cooperates with a fixed electrode on the cavity surface to form a capacitor therewith whose value varies as a function of diaphragm deflection in response to an applied pressure.

Abstract: An ultrasonic echo-ranging meter for measuring the changing level of liquid in a tank or open channel, the meter including a transducer at a raised position above the liquid surface. Pulses of ultrasonic energy transmitted by the transducer are directed toward the liquid surface and reflected thereby to produce main echo pulses that are picked up by the same transducer. The round trip transmit time of the pulse energy in the gaseous medium above the liquid depends on the distance between the transducer and the liquid surface, this time being measured to provide a reading of liquid level. Also intercepted by the transducer are parasitic echo pulses originating from reflecting wall surfaces and other obstacles in the vicinity of the tank or channel, which parasitic pulses may be confused with the main echo pulses and result in an erroneous reading.

Abstract: An industrial process control system in which an electronic controller acts in a controlled process subject to process "dead time" to maintain a process variable at a desired value. Applied as inputs to the controller are signals representing the process variable and a set point, the controller yielding an output signal that reflects the deviation of the process variable from the set point and acts to adjust a final control element in the system to cause the process variable to conform to the set point. To effect self-tuning of the controller, a microprocessor is provided which is responsive to the process variable signal and the output signal from the controller and functions while the controller is operating to identify in a discrete-time process model parameter-identifier the process dead time and the process parameters, and to compute tuned controller parameters, and to transfer the calculated controller parameters to the controller so that the controller can be tuned to prevailing process conditions.

Abstract: Computer graphics for an industrial process installation or other computer-controlled system in which the system is graphically displayed on the screen of the computer terminal. Each controllable element in the system, such as a valve, a control dial or a switch, is marked on the display by an action point. In order for an operator to select any desired action point on the display to carry out an action appropriate thereto, a cursor is provided which can be manipulated by a key matrix to occupy a position coinciding with any action point thereon. The key matrix is a three-by-three-matrix constituted by a home key surrounded by eighty arrow keys whose arrows are directed to the major axes of a compass rose. Only one action point can be selected at a time. The selected point then effectively becomes the compass center, the previously selected point being then de-selected.

Abstract: A telemetering system wherein a transmitting device responsive to an input signal derived from a sensor representing a metered variable, such as temperature or flow rate, is adapted to generate a corresponding direct-current signal. This signal is conveyed over a two-wire line to a receiving station through a terminal resistor across which a voltage signal is developed corresponding to the incoming current signal. The receiving station includes a DC power supply whose output is fed over the same two-wire line to the transmitting device to provide operating power therefor. In order to enhance the power available to the transmitting device, the current signal generated by the transmitting device lies in a 0% to 100% signal range in which the ratio of direct-current I.sub.o at 0% signal to direct-current I.sub.100 at 100% signal is greater than 1/5 or 0.2.

Abstract: A converter for converting a variable data frequency which lies in a low frequency range whose upper limit is about 200 Hz to a corresponding digital value. The converter includes an electronic counter having an enabling input and a count input. Derived from the data frequency is a data signal whose frequency is a given sub-multiple of the data frequency as selected by a digital computer. The data signal is applied to the enabling input to enable the counter for a period equal to the duration of a half cycle of the incoming data signal. Derived from an electronic clock operating at a constant frequency above 10,000 Hz is a clock signal whose pulse repetition rate is a given sub-multiple thereof as selected by the computer. These clock pulses are applied to the count input of the counter whereby the count accumulated therein is determined by the duration of the enabling period.

Abstract: A magnetic flowmeter in which a fluid to be metered is conducted through a ceramic spool coaxially supported within a cylinder casing to define an inner chamber. Mounted within the chamber at opposing positions on a magnet axis perpendicular to the longitudinal flow axis of the spool are a pair of electromagnets to establish an electromagnetic field in the spool whose lines of flux are intercepted by the fluid to induce a voltage therein. Interposed between the electromagnets and the outer surface of the spool and conforming to and secured to this surface are a pair of flexible printed circuit boards which are so printed as to define capacitance metering electrodes at diametrically-opposed positions on the spool on an electrode axis at right angles to the magnet axis and at right angles to the longitudinal flow axis, whereby the voltage induced in the fluid is picked up by these electrodes to produce a signal which depends on the flow rate of the fluid.

Abstract: An electromagnetic flowmeter having a frame assembly formed by an octagonal metal frame within which are mounted a pair of electromagnets and a pair of electrode holders. The electromagnets are secured to one set of opposing sides of the frame along a first transverse axis which passes through the geometric center of the frame while the holders are secured to another set of opposing sides along a second tranverse axis which passes through the center at right angles to the first axis. The frame assembly is encapsulated within a generally cylindrical plastic insulating body of polymeric material having a longitudinal bore therein defining a flow conduit whose flow axis passes through the geometric center of the frame and is perpendicular both to the first and second transverse axes whereby when the fluid flows therethrough it intersects the magnetic lines of flux produced by the electromagnets.

Abstract: An electromagnetic flowmeter in which the fluid being metered is conducted through a flow tube having a pair of electrodes, the fluid intersecting a magnetic field whereby the resultant voltage induced in the fluid is transferred to the electrodes to provide a signal indicative of flow rate. The magnetic field is created by a pair of electromagnets at diametrically-opposed positions on the flow tube to produce lines of magnetic flux thereacross. These electromagnets are driven by a low-frequency pulsatory wave, each periodic cycle of which is constituted by an excitation pulse of brief duration and high amplitude followed by a relaxation interval of relatively long duration so that the resultant duty cycle is low. Because the average power consumed by the electromagnets is at a very low level, this makes it possible to power the flowmeter from a remote station through a two-wire transmission line which also conveys the signal to the station.

Abstract: A mass flowmeter of the Coriolis-type in which the fluid to be metered is conducted through a loop supported on a stationary frame, the loop having a natural resonance frequency. Mounted at the vertex of the loop is a ballistic vibrator which is electrically energized to cause the loop to vibrate at its natural frequency on either side of its static plane. The fluid passing through the loop is subjected to Coriolis forces, causing the vibrating loop to torsionally oscillate in accordance with the mass flow rate of the fluid. This torsional oscillation is sensed by a pair of strain gauge transducers mounted in balanced relation on opposite legs of the loop, whereby the signals yielded by the transducers have a difference in magnitude therebetween that depends on the amplitude of the torsional oscillation. These signals are applied to a differential amplifier whose output is proportional to the mass flow rate of the fluid.

Abstract: A differential pressure-transducer of the capacitive type that includes a drum-shaped insulating body whose flat opposing faces each have a circular back-up nest indented therein covered by an insulating diaphragm to define a cavity. The underside of each diaphragm is metallized as is the base of the related nest to form the electrodes of a variable capacitor whose value depends on the degree and direction of diaphragm deflection. Interconnecting the cavities is a plurality of internal ducts of small diameter that extend between the bases of the nests. Admitted through one of the ducts and filling the cavities is an incompressible dielectric fluid. Hence when an increase in high pressure applied to the face of one diaphragm acts to deflect this diaphragm inwardly, the fluid in the related nest is forced through the ducts into the nest for the low pressure diaphragm which is then deflected outwardly.

Abstract: A mass flowmeter of the Coriolis type in which the fluid to be metered is conducted through a pipe which is coiled to form a double loop. The pipe is anchored at its inlet and outlet ends and also at its center which is the junction of the two loops to define a tuning fork in which the identical loops on either side of the anchored center function as tines that are free to vibrate as well as to twist. An electromagnetic driver mounted at the vertex of the double loop is electrically energized to cause the loops to vibrate in phase opposition at the natural frequency of the tuning fork. The fluid passing through the double loop is subjected to Coriolis forces, thereby causing the vibrating loops to torsionally oscillate in accordance with the mass flow of the fluid.

Abstract: A front display panel for an industrial process control instrument which acts to maintain a process variable, such as flow rate, at a desired value. The instrument compares a signal representing the variable with an adjustable set point to produce an output signal that reflects the deviation of the variable from the set point, the output signal being applied to a final control element such as a valve which governs the process variable. The front panel of the instrument includes a bar graph indicator for the process variable, a bar graph indicator for the set point and a bar graph indicator for the output signal, all three indicators being of the gas discharge type and being integrated into a single panel defining a sealed envelope filled with an ionizable gas and provided with electrodes. Also integrated into the panel are touch-sensitive switches and other control and indicating elements.

Abstract: An electromagnetic flowmeter in which the fluid being metered is conducted through a flow tube having a pair of electrodes, the fluid intersecting a magnetic field whereby the resultant voltage induced in the fluid is transferred to the electrodes to provide a signal indicative to flow rate. The magnetic field is created by a pair of pole pieces formed of "hard" magnetic material. The pieces are placed at diametrically-opposed positions and are magnetically interconnected to define a magnetic circuit. Excitation pulses which alternate in polarity are periodically applied by respective magnet drivers to coils wound about the pole pieces to alternately magnetize the pieces in one direction and remagnetize the pieces in the reverse direction, thereby establishing the desired field. The duty cycle of the pulses is such as to reduce the average power requirements to a very low level.

Abstract: A set of nested graphics for a computer-controlled industrial plant or any other complex system having several interrelated sections. The nested set includes a graphic having entry points thereon each providing access to respective other graphics in the set. These have entry points thereon which provide access to still other graphics so that paths can be established interconnecting the various graphics in the set. The operating mechanism is such that when a cursor is positioned on a given entry point in one graphic being displayed and a SELECT button is pressed, access is then had to a second graphic corresponding to the selected point; and when a NEXT key is operated, this second graphic is displayed. When the cursor is then positioned on an entry point in the displayed second graphic and the SELECT button is pressed, access is had to a third graphic corresponding to the selected entry point, which third graphic is displayed when the NEXT key is operated.

Abstract: An electromagnetic flowmeter in which the fluid being metered passes through a flow tube to intersect the lines of flux of a magnetic field produced by an electromagnet whereby the resultant voltage induced in the fluid is transferred to a pair of electrodes mounted at diametrically-opposed positions on the tube. The electromagnet is so driven as to produce a flux field having a triangular wave form. The voltage signal yielded by the electrodes is therefore a composite having a triangular wave component that is a replica of the flux wave and a rectangular wave component that is generated by a spurious loop pick up voltage. The composite signal is applied to a converter and processed therein to cancel out the rectangular wave component whereby the converter output signal is accurately proportional to the flow rate of the fluid.

Abstract: A mass flowmeter of the Coriolis-type in which the fluid to be metered is conducted through a loop supported on a stationary frame, the loop having a natural resonance frequency. Mounted at the vertex of the loop is a ballistic vibrator which is electrically energized to cause the loop to vibrate at its natural frequency on either side of its static plane. The fluid passing through the loop is subjected to Coriolis forces, causing the vibrating loop to torsionally oscillate in accordance with the mass flow rate of the fluid. This torsional oscillation is sensed by a pair of strain gauge transducers mounted in balanced relation on opposite legs of the loop, whereby the signals yielded by the transducers have a difference in magnitude therebetween that depends on the amplitude of the torsional oscillation. These signals are applied to a differential amplifier whose output is proportional to the mass flow rate of the fluid.

Abstract: A magnetic flowmeter which includes a spool formed by a metallizable ceramic whose dielectric constant is at least 25 through which the fluid to be metered is conducted. The outer surface of the spool is metallized in its central region to define a pair of capacitative metering electrodes at diametrically-opposed positions, an electromagnetic field being established within the spool whereby when the flowing fluid intercepts this field, an emf is induced therein to produce a signal at the metering electrodes which is a function of flow rate. Overlying each metering electrode and projecting from the spool is a ceramic block whose outer surface is metallized to define a shield electrode which covers the metering electrode.