Abstract: In an oxygen analyzer for an industrial process, an automotive type oxygen sensor has a sensor element assembly with an outer thin walled shield containing insulation and surrounding the sensor element of the automotive type oxygen sensor.

Abstract: A process and apparatus for shadowing memory uses a single memory chip which is addressable into an address field which is smaller than the memory chip. A program having a main control portion is programmed into a main memory area of the memory chip and is directly connected to a main address space of the address field. The program also includes a plurality of secondary program portions which can be used one at a time with the main control portion of the program. Each of the secondary program portions is stored in a separate secondary and shadowed memory area of the memory chip. A secondary address space of the address field which is large enough to accommodate only one secondary memory area at a time, is controlled so as to be latched to only one secondary memory area at a time. Latching is achieved through higher bits of address locations in a selected portion of the address field.

Abstract: A magnetic actuator for adjusting the zero and span settings of a transmitter used in industrial process control systems. The actuator has a single magnet in a housing. The actuator is removable from the transmitter.When the actuator is unactuated the magnet is in a null position wherein it does not actuate either the zero or span setting reed switches. The magnet can be moved to either a first position wherein it actuates the zero setting reed switch or a second position wherein it actuates the span setting reed switch. The actuator applies a torque in the proper direction to return the magnet to the null position when the torque applied to move the magnet to either the first or second position is removed.

Abstract: A digital FSK transmitter utilizing a clock feedback signal driving an accumulator to operate a pair of registers having a pair of preset numbers stored therein to selectively add said numbers through a binary adder to the accumulator to output the FSK signal thereby.

Abstract: A cover lock assembly for a process transmitter having threadably removable end caps and corrugated outer surfaces is provided for engaging the corrugated surfaces by way of a toothed cover lock which is removably affixed to the transmitter housing.

Abstract: A device which is a combination of a method and apparatus and a filter, such as but not limited to, a conventional lag filter for digitally processing and filtering signals used in industrial control applications. The method and apparatus provides a factor which is used by the filter to process the digital signal at the input to the device. The method determines if the change in the input signal is either due to noise or a valid signal change. Information which gives a past analysis of the trend in direction of the signal at the input to the device is used in the method. The trend information includes a factor representative of the past history of the trend. The method uses the most recent trend indicator to determine to a reasonable degree of confidence if the signal currently at the input to the device is or is not characteristic of noise. If the signal at the input is not believed to be characteristic of noise, then the method adjusts the trend indicator by a tracking credit.

Abstract: An industrial process oxygen analyzer, and method of using same, incorporates an automotive oxygen sensor to minimize the criticalness of controlling heater temperature during operation. Higher sensor heater temperature, required to accommodate the automotive oxygen sensor, is achieved by application of higher supply voltage to the sensor heater. Current limiting of the heater supply circuit reduces stress on the sensor heater, even at the higher operating temperature.

Abstract: A digital FSK receiver includes a zero-crossing detector which detects the zero crossings in an FSK signal having at least two signal frequencies. The time interval between zero crossings is then measured with a first interval value corresponding to one of the signal frequencies and a second interval value corresponding to the other signal frequency. An accumulator outputs a digital signal which depends on whether the interval is at the first value or the second value, the digital signal including logical zeros and ones.

Abstract: The characteristics of the field process system controlled by a self tuning controller are obtained by analyzing the open loop response of the process variable to a step applied at the controller's control output. A first-order system response with pure time delay is used to approximate a higher-order field process system's actual response. The overall deadtime and time constant of the first-order approximation are determined. The maximum slope of the process variable response to the step is stored along with an assigned time of its occurrence and an assigned process variable. The stored information is used to approximate the overall deadtime. In one embodiment the stored information is assumed to be the data obtained from a second-order response having a 10:1 time constant ratio and is used to find the assumed second-order time constants which are used to find the first-order time constant.

Abstract: The firing rate and the feedwater flow rate of a universal pressure boiler are controlled using a cascaded steam temperature control system. The secondary superheater outlet temperature comprises an outer loop for the control system, while the convection pass outlet temperature comprises an inner loop for the control system. Control variables for the system include the secondary superheater outlet temperature, the convection pass outlet temperature and the difference between the primary superheater outlet temperature and the secondary superheater inlet temperature.

Abstract: A pneumatic servo comprises a motor having a shaft for rotation in response to an electrical signal. A cam is connected to the shaft for rotation therewith. The cam has an outer profiled periphery and opposite sides. A pneumatic nozzle having an opening for directing a flow of gas toward one side of the cam near the periphery, obscures the flow by different amounts as the cam rotates to create a back pressure in the nozzle comprising a pneumatic signal. A curved projection engages an opposite side of the cam, the projection being aligned with the nozzle opening and reducing oscillation excursions of the servo at gas pressures in the nozzle of above 12 psi.

Abstract: A neural network control based on a general multi-variable nonlinear dynamic model incorporating time delays is disclosed. The inverse dynamics of the process being controlled is learned represented by a multi-layer neural network which is used as a feedforward control to achieve a specified closed loop response under varying conditions. The weights between the layers in the neural network are adjusted during the learning process. The learning process is based on minimizing the combined error between the desired process value and the actual process output and the error between the desired process value and the inverse process neural network output.

Abstract: A plant loop communication system utilizing a plurality of Loop Interface Slave (LIS) modules, each of which being an intelligent slave module incorporating its own microprocessor, is described. The use of such a module permits off-load processing so that receiving, transmitting and message processing cam occur simultaneously. A Superloop Bus Module (SBM) contains a data base which allows the asynchronous operation of the system. A Superloop Storage Module (SSM) stores data for transmission onto the loop and/or incoming data for transmission to an operator console.

Abstract: An arrangement for providing radio frequency and electromagnetic interference protection to at least part of circuitry mounted on a circuit board comprises alternating slots and bridges which form a boundary between a protected area of the circuit board and an unprotected area of the circuit board. The circuit portions which require protection are mounted in the protected area and are covered by a top cover having fingers which extend through the slots. Connecting lines between the protected and unprotected portions of the circuit portions extend along the bridges between the slots. A bottom cover engages under the protected area and mates to the top cover for providing electromagnetic interference protection for the circuit portions within the protected area.

Abstract: A method of estimating pH titration curves for use in the adaptive control of pH in a process, comprises gathering data points which each represent the ratio between a reagent added to the process and a flowrate to the process at a measured pH, storing the data points in a bin system according to pH, and using the stored data points to create a model of the titration curve for use in controlling the addition of reagent. Older points are replaced by newer points during the process to continuously update the model. The model was used to generate a gain schedule for operating a PI controller that is used in adding a reagent to the process.

Abstract: A method and device for measuring energy in fuel gas comprises a solid electrolyte oxygen pump for generating an amount of oxygen in response to current being supplied to the pump. A sample of the gas is mixed with the oxygen from the pump to produce a mixture which is subjected to complete combustion in a catalytic combustor. An oxygen sensor is connected to the catalytic combustor for measuring excess oxygen in the exhaust gas from the combustor. A signal from the oxygen signal is compared to a known and desired amount of excess oxygen in the exhaust gas. If there is too much or too little oxygen inthe exhaust gas, a feedback signal is used to adjust the amount of current being supplied to the oxygen pump until the actual amount of excess oxygen is equal to the selected amount of excess oxygen. The selected amount of excess oxygen is indicative of complete combustion of the sample mixture.