Abstract: A system for and a method of managing a communications network through the use of multiple network connections. The system prepares at least two transport service providers of a node for establishing a network connection with corresponding transport service providers of another node and associates the at least two transport service providers with each other and with a requesting application. The system monitors network connection condition and determines availability and suitability of each network connection. The system selectively transmits information via a selected network connection. The system seamlessly establishes the multiple connections and transmits the information over the selected network connection and is transparent to the application.

Abstract: A pressure transducer having a redundant fluid pressure sensor can be used to determine if the pressure transducer needs to be recalibrated. The pressure transducer comprises a fluid pressure sensor for measuring differential pressure. The fluid pressure sensor includes a pair of substantially identical pressure sensors for providing a variable electrical output as a function of a differential fluid pressure and a reference sensor for providing an electrical output independent of the differential fluid pressure. A conditioning circuit is provided for generating a frequency-based signal whose frequency is a function of the electrical output for each fluid pressure sensor. The electrical output of the first and second pressure sensors can be compared to determine whether the pressure transducer needs to be calibrated. In one embodiment, the pressure sensors comprise variable capacitors.

Abstract: A pressure transducer having a redundant fluid pressure sensor can be used to determine if the pressure transducer needs to be recalibrated. The pressure transducer comprises a fluid pressure sensor for measuring differential pressure. The fluid pressure sensor includes a pair of substantially identical pressure sensors for providing a variable electrical output as a function of a differential fluid pressure and a reference sensor for providing an electrical output independent of the differential fluid pressure. A conditioning circuit is provided for generating a frequency-based signal whose frequency is a function of the electrical output for each fluid pressure sensor. The electrical output of the first and second pressure sensors can be compared to determine whether the pressure transducer needs to be calibrated. In one embodiment, the pressure sensors comprise variable capacitors.

Abstract: A system and method for process instrumentation and control equipment. The system including a paperless, microprocessor-based, panelboard recorder having built-in data acquisition functions, a mechanism for archiving data, and a variety of display types. Memory space is conserved by deriving quantized data comprising signal samples received at a first rate and storing them for a first relatively short period in a fine quantized memory, and storing in a coarse memory, for a longer period of time, a subset of said signal samples recurring at a rate lower than the first set and having fewer quantized levels than the first set of samples. The operator can then determine whether coarse data obtained over a relatively long period or fine data obtained over a shorter period are displayed.

Abstract: A pressure transducer having a redundant fluid pressure sensor can be used to determine if the pressure transducer needs to be recalibrated. The pressure transducer comprises a fluid pressure sensor for measuring differential pressure. The fluid pressure sensor includes a pair of substantially identical pressure sensors for providing a variable electrical output as a function of a differential fluid pressure and a reference sensor for providing an electrical output independent of the differential fluid pressure. A conditioning circuit is provided for generating a frequency-based signal whose frequency is a function of the electrical output for each fluid pressure sensor. The electrical output of the first and second pressure sensors can be compared to determine whether the pressure transducer needs to be calibrated. In one embodiment, the pressure sensors comprise variable capacitors.

Abstract: A monolithic temperature and pressure transducer having a plurality of capacitive sensors. The capacitors are formed from the same silicon substrate and are equally affected by temperature variations, including temperature gradients.

Abstract: In a distributed process-control system, program-controlled apparatus is provided for permitting an operator to control the mode of a Sequential Function Chart (SFC) to place the Chart in any of five different modes as a convenience in monitoring, editing and/or changing the SFC program. These modes are: OFF mode, for temporarily disabling operation of the SFC Chart, an AUTO mode which allows the SFC program and Chart to run as configured, a HOLD mode which freezes the chart in its current state, a MANUAL mode enabling the operator to force the Chart to an operator-selected step while the output of the current step is maintained active, and a TRACE mode enabling the operator to view the steps in the Chart sequentially, and to force the steps without executing them.

Abstract: A vent system which provides constant venting of air through a vent opening in a casing while preventing water from reaching the vent opening and entering the casing, even water from a high-speed jet of water. The vent system is mounted in the vent opening and provides a tortuous path for air between the vent opening and ambient. A central tube contains openings communicating with the interior of a surrounding baffle tube, about half-way along the length of the inner tube, and the baffle tube permits air to pass around its ends between its interior and a surrounding central chamber. End chambers are provided at each end of the central chamber, each communicating with the central chamber. The end chambers have slots in their edges which communicate with ambient, and through which a high-speed jet of water may enter. The water, for the most part, enters one slot, traverses the end chamber, and exits through one or both of the other slots.

Abstract: Switching power supplies for low power circuits. Power supplies described and disclosed herein comprise a linear regulator for regulating an input power to this power supply, a flyback regulator with three modes of output control comprising indirect sense feedforward, feedback, and override control. Indirect sense feedforward responds to changes in input voltage. The feedback responds to changes in output voltage with use of both of these wide variations in input voltage and output load can be tolerated. The override control takes over during abnormal conditions such as startup and short circuit. Switching power supplies described herein have high efficiencies and provide efficient power management, especially in low power budget applications.

Abstract: Integrated transmitters and controllers for use in monitoring process variables. A transmitter and controller for monitoring and controlling a process variable in a process control loop comprises a transmitter for producing a digital signal indicative of the process variable's state, and a digital controller supplied with the digital signal from the transmitter responsive to the digital signal, and further interfaced in a process control loop for controlling the process variable in response to the digitally communicated signal from the transmitter. Integrated transmitters and controllers described herein simplify installation and maintenance of industrial process control systems and place the controller functions at the process variable, thereby increasing control system efficiency.

Abstract: Imbalances between currents to and from a remote point are detected by passing the outgoing currents and the return current through different, oppositely-oriented coils on a saturable core, and an excitation current is applied to another coil in the same core sufficient to drive the core into saturation in at least one direction. When the outgoing and return currents are the same, the excitation produces successive voltage pulses of the same durations, as measured by an up-down counter; if an imbalance is present, the remainder in the up-down counter shows this. To detect excessively high imbalances, which might place the core always in saturation, another counter preferably senses the sum of the widths of successive pulses, and indicates an imbalance if this sum falls below a preselected threshold.

Abstract: Low power oscillator circuits for providing clock signals. The circuits comprise crystal oscillators for providing an input wave form of a specified frequency to the clock circuit, square wave generators having at least two input terminals wherein one of the two input terminals is coupled to the oscillator, and a power output network coupled to the square wave generator for outputting a substantially square wave having substantially the same frequency as the input wave form, the power output network being biased at a high voltage level. Clock circuits described herein provide the advantage of low power oscillation with little power dissipation.

Abstract: The ratio C.sub.1 /C.sub.2 between the capacitances of two capacitors is obtained by connecting them into the frequency-determining circuit of an oscillator in at least three different combinations, namely C.sub.1 along, C.sub.2 along and both or neither of C.sub.1 and C.sub.2 ; the resultant oscillation frequencies are measured, and a signal representative of changes in C.sub.1 /C.sub.2 is derived from the oscillator frequencies, preferably by means of digital circuitry. In one preferred mode C.sub.1 /C.sub.2 is obtained by forming signals proportional to ##EQU1## and in another preferred mode proportional to ##EQU2## In still another preferred mode C.sub.1 /C.sub.2 -1 is obtained from the expression T.sub.1 -T.sub.3 /T.sub.2 -T.sub.3 and used as the indication of changes in C.sub.1 /C.sub.2. In the foregoing, f.sub.1, f.sub.2, f.sub.3 and f.sub.4 are the oscillator frequencies produced respectively by connecting C.sub.1 alone, C.sub.2 along, neither C.sub.1 nor C.sub.2, and both C.sub.1 and C.sub.

Abstract: A flowmeter for liquids is provided having a through passageway for the flow to be measured with a fluid interaction chamber and feedback means to provide an oscillation of the flow. The frequency of this oscillation is linearly and proportionally related to volume rate of flow and is independent of all fluid properties in the turbulent range, i.e., the frequency for a given volume flow rate will be the same for any liquid as long as the flow is turbulent. Provisions are made for detecting this oscillation and a sensor is provided which is responsive to changes in the heat transfer rates to the surrounding media. Vent means is provided communicating with the feedback means for venting gaseous material from the feedback passageways so that the flowmeter can be mounted and operate properly in a vertical pipe section.

Abstract: A calibrating device is disclosed for insertion between a control station and its indicators, preferably of the bar graph type, with provisions for establishing accurate reference voltages available at marked jacks for use and specifically for checking the calibration of the indicating elements, and to provide for utilization of one or both indicators as a precision voltmeter for checking the potential of various points in the circuitry. Provisions are also made for bypass plugging in so that the indicators operate in a normal manner as if the calibrator were not present. The normal jacks also provide convenient access to the set-point and variable voltage of the station and facilitate the measuring of these voltages by an external digital voltmeter if desired.

Abstract: A stepper motor control system is described for positioning a mechanical element connected to a stepper motor which includes an electric analog signal producing system connected to a stepper motor with a variable speed mode of driving the motor and which includes a power saver circuit for electrical de-energization of the motor when not in use.

Abstract: A fluid pressure reproducing relay is described having a high order of accuracy in matching the output pressure to the loading pressure under steady state conditions, having a large flow capacity for both supply and exhaust and which is small in size for its capacity, the relay having a resilient rolling seal with a vented seating arrangement that requires no clamping, having a stabilizing mass loosely attached to a force balance diaphragm assembly and in which a balanced area supply plunger is employed.

Abstract: An isolation circuit with duty cycle feedback is disclosed which includes an operational amplifier with capacitive coupled negative feedback such that its output voltage varies to maintain its input terminals at the same potential, and which output is connected to the control terminal of a voltage controlled oscillator which generates a square wave voltage in which the ratio of ON time to the total period is directly related to the voltage from the operational amplifier. The output pulses of the voltage controlled oscillator are fed through a resistor to the negative input terminal of the operational amplifier. The output pulses from the oscillator are also fed through a driver transistor to control the input of an opto-coupler. The output from the opto-coupler passes through an amplifier to produce a square wave voltage with the same ON time ratio as the voltage controlled oscillator.

Abstract: A control circuit for bar graph display panels is described which reduces the tendency to drift, which obviates the necessity of maintaining an absolutely constant oscillator frequency and an absolutely constant ramp rate by utilizing a feedback system to reference the ramp end points to a single precise voltage.

Abstract: A pressure to electric transducer is described employing an electrical capacitance formed by two parallel metal plates separated by a variable air gap, one of the plates being fixedly mounted and the other being movable to change the spacing in direct proportion to fluid pressure acting on an input element or capsule to which the movable plate is connected. The capacitance forms one leg of a negative feed back divider network, for controlling an operational amplifier so that its gain is directly proportional to the spacing of the plates. The amplifier is driven by a constant alternating current source so that its output is directly proportional to the applied pressure. The voltage output can be rectified and transformed in a conventional manner for transmission of a signal.