Industrial process control apparatus

Claim 2

A process control system comprising, in combination, a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under program control to process input data supplied thereto; transmission means for directing said measurement signals to said central computer means; said computer means including input multiplexing means to receive said measurement signals and to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said central computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals; signalling means forming part of said central computer means to receive said computed answer signals and to produce corresponding electrical pulses having a characteristic the magnitude of which is proportional to the computed answer signals respectively; output multiplexing means forming part of said central computer means and operable with said signalling means to distribute corresponding output pulse signals to a set of output circuits respectively; an electronic storage device for each of said output circuits to receive said output pulse signals and comprising a memory capacitor with a high-gain amplifier connected thereto, the capacitive charge remaining at a substantially constant level during the times intervening the receipt of said output pulse signals; means coupled to the output of each of said storage devices for developing a control signal corresponding to the charge stored in the respective memory capacitor; and output transmission means for sending said control signals to corresponding operating elements of the process.

Claim 3

A process control system comprising, in combination, a plurality of condition-sensing devices operatively associated with the process, said devices being arranged to produCe DC signals the magnitudes of which are proportional to the respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under a stored program to process input data supplied thereto; transmission lines for directing said DC measurement signals to said central computer means; input multiplexing means forming part of said computer means to receive said DC measurement signals and periodically produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; circuit means for directing said sample signals to said computational section of said central computer so that the latter can carry out THE programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed process instruction signals; pulse-length signalling means forming part of said central computer means to receive said computed process instruction signals and to produce corresponding electrical pulses the time durations of which are proportional to the computed process instruction signals respectively; output multiplexing means forming part of said central computer means and operable with said pulse-length signalling means to distribute to a corresponding set of output circuits respective output pulse signals the magnitudes of which are constant and the time durations of which are equal to the time durations of said electrical pulses; an electronic integrator for each of said output circuits to receive said output pulse signals, each integrator comprising a high-gain amplifier having an input resistor and a negative feedback capacitor, said amplifier serving to maintain the capacitive charge at a substantially constant level during the times intervening the receipt of said output pulse signals; means coupled to the output of each of said integrators for developing a continuous DC control signal having a magnitude corresponding to the charge stored in the respective feedback capacitor; and output transmission means for sending said control signals to corresponding operating devices for adjusting the measured process conditions individually to the desired levels in accord with the calculations of said computer means.

Claim 4

A process control system comprising, in combination, a plurality of condition-sensing devices operatively associated with the process, said devices being arranged to produCe DC signals the magnitudes of which are proportional to the respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under a stored program to process input data supplied thereto; transmission lines for directing said DC measurement signals to said central computer means; input multiplexing means forming part of said computer means to receive said DC measurement signals and periodically produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; circuit means for directing said sample signals to said computational section of said central computer so that the latter can carry out THE programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed process instruction signals; pulse-length signalling means forming part of said central computer means to receive said computed process instruction signals and to produce corresponding electrical pulses the time durations of which are proportional to the computed process instruction signals respectively; output multiplexing means forming part of said central computer means and operable with said pulse-length signalling means to distribute to a corresponding set of output circuits respective output pulse signals the magnitudes of which are constant and the time durations of which are equal to the time durations of said electrical pulses; an electronic integrator for each of said output circuits to receive said output pulse signals, each integrator comprising a high-gain amplifier having an input resistor and a negative feedback capacitor, said amplifier serving to maintain the capacitive charge at a substantially constant level during the times intervening the receipt of said output pulse signals; means coupled to the output of each of said integrators for developing a continuous DC control signal having a magnitude corresponding to the charge stored in the respective feedback capacitor; and output transmission means for sending said control signals to corresponding operating devices for adjusting the measured process conditions individually to the desired levels in accord with the calculations of said computer means.

Claim 5

A process control system comprising, in combination, a plurality of condition-sensing devices operatively associated with the process, said devices being arranged to produce measurement signals the magnitudes of which are proportional to the respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under a stored program to process input data supplied thereto; transmission means for directing said measurement signals to said central computer means; input multiplexing means forming part of said computer means to receive said measurement signals and periodically produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; circuit means for directing said sample signals to said computational section of said central computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed process instruction signals; pulse-length signal-generating means forming part of said central computer means to receive said computed process instruction signals and to produce corresponding electrical pulses the time durations of which are proportional to the computed process instruction signals respectively; output multiplexing means forming part of said central computer means and operable with said pulse-length signal generating means to distribute to a set of output circuits respective output pulse signals the magnitudes of which are constant, the time durations of which are equal to the time durations of said electrical pulses, and the polarities of which signify the direction of thE required change calculated by said central computer; an electronic integrator for each of said output circuits to receive said output pulse signals, each integrator comprising a high-gain amplifier having an input resistor and a negative feedback capacitor, said amplifier serving to maintain the charge on said capacitor at a substantially constant level during the times intervening the receipt of said output pulse signals; manual signal supply means providing fixed magnitude signals of opposite polarities; switch means for each of said output circuits for disconnecting the output pulse signals from said integrators, said switch means including means selectively operative to connect to the integrator either of said fixed-magnitude signals to afford a manual control over the charge on the respective capacitor; means coupled to the output of each of said integrators for developing a continuous DC control signal having a magnitude corresponding to the charge stored in the respective feedback capacitor; and output transmission means for sending said control signals to corresponding operating devices for adjusting the measured process conditions to the proper levels as calculated by said central computer means.

Claim 6

A process control system comprising, in combination, a plurality of condition-sensing devices operatively associated with the process, said devices being arranged to produce measurement signals the magnitudes of which are proportional to the respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under a stored program to process input data supplied thereto; transmission means for directing said measurement signals to said central computer means; input multiplexing means forming part of said computer means to receive said measurement signals and periodically produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; circuit means for directing said sample signals to said computational section of said central computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed process instruction signals; pulse-length signal-generating means forming part of said central computer means to receive said computed process instruction signals and to produce corresponding electrical pulses the time durations of which are proportional to the computed process instruction signals respectively; output multiplexing means forming part of said central computer means and operable with said pulse-length signal generating means to distribute to a set of output circuits respective output pulse signals the magnitudes of which are constant, the time durations of which are equal to the time durations of said electrical pulses, and the polarities of which signify the direction of thE required change calculated by said central computer; an electronic integrator for each of said output circuits to receive said output pulse signals, each integrator comprising a high-gain amplifier having an input resistor and a negative feedback capacitor, said amplifier serving to maintain the charge on said capacitor at a substantially constant level during the times intervening the receipt of said output pulse signals; manual signal supply means providing fixed magnitude signals of opposite polarities; switch means for each of said output circuits for disconnecting the output pulse signals from said integrators, said switch means including means selectively operative to connect to the integrator either of said fixed-magnitude signals to afford a manual control over the charge on the respective capacitor; means coupled to the output of each of said integrators for developing a continuous DC control signal having a magnitude corresponding to the charge stored in the respective feedback capacitor; and output transmission means for sending said control signals to corresponding operating devices for adjusting the measured process conditions to the proper levels as calculated by said central computer means.

Claim 7

A process control system comprising, in combination, a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under a program control to process input data supplied thereto; transmission means for directing said measurement signals to said central computer means; said computer means including input multiplexing means to receive said measurement signals and periodically to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said central computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals; pulse-length signalling means forming part of said central computer means to receive said computed answer signals and to produce corresponding electrical pulses the time durations of which are proportional to the computed answer signals respectively; output multiplexing means forming part of said central computer means and operable with said pulse-length signalling means to distribute corresponding output pulse signals in sequence to a group of output circuits respectively; a group of switches each having a control terminal connected in one of said output circuits and actuable in sequence by said output pulse signals; DC power supply means; connection means operable by said pulse-length signalling means for connecting the input of each actuated switch to said DC power supply means during the time of such switch actuation, said connection means operating to disconnect the inputs of said switches from said DC power supply means when no switch is actuated; a group of electronic integrators each having an input connected to the output terminal of a respective one of said switches, each integrator comprising a memory capacitor with a high-gain amplifier connected thereto to maintain the capacitive charge at a substantially constant level during the times intervening the receipt of the DC pulse signals from the outputs of said switches; means coupled to the output of each of said integrators for developing a control signal corresponding to the charge stored in the respective memory capacitor; and output transmission means for sending said control signals to corresponding operating elements of the process.

Claim 8

A process control system comprising, in combination, a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under a program control to process input data supplied thereto; transmission means for directing said measurement signals to said central computer means; said computer means including input multiplexing means to receive said measurement signals and periodically to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said central computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals; pulse-length signalling means forming part of said central computer means to receive said computed answer signals and to produce corresponding electrical pulses the time durations of which are proportional to the computed answer signals respectively; output multiplexing means forming part of said central computer means and operable with said pulse-length signalling means to distribute corresponding output pulse signals in sequence to a group of output circuits respectively; a group of switches each having a control terminal connected in one of said output circuits and actuable in sequence by said output pulse signals; DC power supply means; connection means operable by said pulse-length signalling means for connecting the input of each actuated switch to said DC power supply means during the time of such switch actuation, said connection means operating to disconnect the inputs of said switches from said DC power supply means when no switch is actuated; a group of electronic integrators each having an input connected to the output terminal of a respective one of said switches, each integrator comprising a memory capacitor with a high-gain amplifier connected thereto to maintain the capacitive charge at a substantially constant level during the times intervening the receipt of the DC pulse signals from the outputs of said switches; means coupled to the output of each of said integrators for developing a control signal corresponding to the charge stored in the respective memory capacitor; and output transmission means for sending said control signals to corresponding operating elements of the process.

Claim 9

A system as claimed in claim 4, wherein said DC power supply means includes both positive and negative voltages; and means controlled by said computer means answer signal for selectively connecting said positive or negAtive voltage to the associated switch input.

Claim 10

A system as claimed in claim 5, wherein said DC power supply means consists of two DC power sources connected in series; first and second switches having their input terminals connected respectively to the remote terminals of said two power sources and having their output terminals connected together to the inputs of all of said group of switches; means controlled by said computed answer signals for selectively energizing the control terminal of said first or second switch so as to apply either a positive or a negative signal to the input of the actuated one of said group of switches; and impedance means connecting the common terminals of said two DC power sources to the output terminals of said first and second switches, whereby to assure that the inputs to said group of switches is essentially zero except when one of said switches is actuated.

Claim 11

A process control system comprising, in combination, a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under program control to process input data supplied thereto; transmission circuit means for directing said measurement signals to said central computer means; said computer means including input multiplexing means to receive said measurement signals and periodically to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said central computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals; pulse-length signalling means forming part of said central computer means to receive said computed answer signals and to produce corresponding electrical pulses the time durations of which are proportional to the computed answer signals respectively; output multiplexing means forming part of said central computer means and operable with said pulse-length signalling means to distribute corresponding output pulse signals to a set of output circuits respectively; an electronic integrator for each of said output circuits to receive said output pulse signals and comprising a memory capacitor with a high-gain amplifier connected thereto to maintain the capacitive charge at a substantially constant level during the times intervening the receipt of said pulse signals; means coupled to the output of each of said integrators for developing a control signal corresponding to the charge stored in the respective memory capacitor; output transmission means for sending said control signals to corresponding operating elements of the process; manual supply means switchable into the input of any of said electronic integrators to adjust the charge on said memory capacitor, said manual supply means providing positive or negative voltages selectively to permit increasing or decreasing the charge; and circuit means forming part of said manual supply means to set the effective time-constant of the associated integrator at a value substantially higher than when on automatic control operation.

Claim 12

A process control system comprising, in combination, a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; central digital computer means remote from said sensing devices and including a computational section operating under program control to process input data supplied thereto; transmission circuit means for directing said measurement signals to said central computer means; said computer means including input multiplexing means to receive said measurement signals and periodically to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said central computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals; pulse-length signalling means forming part of said central computer means to receive said computed answer signals and to produce corresponding electrical pulses the time durations of which are proportional to the computed answer signals respectively; output multiplexing means forming part of said central computer means and operable with said pulse-length signalling means to distribute corresponding output pulse signals to a set of output circuits respectively; an electronic integrator for each of said output circuits to receive said output pulse signals and comprising a memory capacitor with a high-gain amplifier connected thereto to maintain the capacitive charge at a substantially constant level during the times intervening the receipt of said pulse signals; means coupled to the output of each of said integrators for developing a control signal corresponding to the charge stored in the respective memory capacitor; output transmission means for sending said control signals to corresponding operating elements of the process; manual supply means switchable into the input of any of said electronic integrators to adjust the charge on said memory capacitor, said manual supply means providing positive or negative voltages selectively to permit increasing or decreasing the charge; and circuit means forming part of said manual supply means to set the effective time-constant of the associated integrator at a value substantially higher than when on automatic control operation.

Claim 13

A system as claimed in claim 7, wherein said manual supply means comprises a center-tapped DC power source adapted to provide either positive or negative signals from the remote terminals thereof; a voltage-dropping resistive network connected across said remote terminals, said network including an even number of resistors greater than two; switch means for establishing connection to any common terminal of said resistors to pick off a corresponding voltage to serve as a manual signal; the ohmic resistances of said resistors being symmetrically arranged so that the positive and negative voltages picked off will be of equal magnitude.

Claim 14

A system as clAimed in claim 8, wherein said network comprises six series resistors, whereby to provide both fast and slow manual operation in either direction.

Claim 15

A process control system comprising, in combination: a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; a central station remote from said sensing devices and including a digital computer having a computational section operating under program control to process input data supplied thereto; transmission means for directing said measurement signals to said computer; said central station including input multiplexing means to receive said measurement signals and to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals; signalling means forming part of said central station to receive said computed answer signals and to produce respective electrical output pulses each having a characteristic the magnitude of which corresponds to the magnitude of the respective computed answer signal; output multiplexing means forming part of said central station and operable with said signalling means to distribute said output pulses to respective control circuits; a capacitor for each control circuit; each control circuit including means for directing to the associated capacitor a signal derived from the corresponding output pulse signal to control the capacitor with charge responsive to the magnitude of said pulse characteristic; and an amplifier connected to each capacitor for developing a control signal for controlling a corresponding operating element of the process in accordance with the charge in the capacitor after the output pulse signal has subsided.

Claim 16

A process control system comprising, in combination: a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; a central station remote from said sensing devices and including a digital computer having a computational section operating under program control to process input data supplied thereto; transmission means for directing said measurement signals to said computer; said central station including input multiplexing means to receive said measurement signals and to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals; signalling means forming part of said central station to receive said computed answer signals and to produce respective electrical output pulses each having a characteristic the magnitude of which corresponds to the magnitude of the respective computed answer signal; output multiplexing means forming part of said central station and operable with said signalling means to distribute said output pulses to respective control circuits; a capacitor for each control circuit; each control circuit including means for directing to the associated capacitor a signal derived from the corresponding output pulse signal to control the capacitor with charge responsive to the magnitude of said pulse characteristic; and an amplifier connected to each capacitor for developing a control signal for controlling a corresponding operating element of the process in accordance with the charge in the capacitor after the output pulse signal has subsided.

Claim 17

Apparatus as claimed in claim 10, including manually operable means for coupling to any of said capacitors positive or negative charging currents to selectively alter the charge on such capacitor and thereby change the control signal produced by the associated amplifier.

Claim 18

A process control system comprising, in combination: a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; a central station remote from said sensing devices and including a digital computer having a computational section operating under program control to process input data supplied thereto; transmission means for directing said measurement signals to said computer; said central station including input multiplexing means to receive said measurement signals and to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals each defining an instruction for an operating element of the process; signalling means forming part of said central station to receive said computed answer signals and to produce respective electrical output pulses each having a controllable characteristic thereof corresponding to the magnitude of the respective computed answer signal; output multiplexing means forming part of said central station and operable with said signalling means to distribute said output pulses to respective output circuits; a capacitor for each output circuit; each output circuit including means for directing to the associated capacitor a signal derived form the corresponding output pulse signal to control the capacitor charge responsive to the magnitude of said pulse characteristic; an amplifier connected to each capacitor for developing a control signal corresponding to the charge stored in the capacitor without significantly altering the charge level during the periods intervening the received pulses; and output transmission means for sending each control signal to a corresponding operating element of the process.

Claim 19

A process control system comprising, in combination: a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; a central station remote from said sensing devices and including a digital computer having a computational section operating under program control to process input data supplied thereto; transmission means for directing said measurement signals to said computer; said central station including input multiplexing means to receive said measurement signals and to produce a series of sample signals representing the magnitudes of said measurement signals sampled in a predetermined order; means for directing said sample signals to said computational section of said computer so that the latter can carry out programmed arithmetic operations with respect to each of said sample signals in sequence and produce corresponding computed answer signals each defining an instruction for an operating element of the process; signalling means forming part of said central station to receive said computed answer signals and to produce respective electrical output pulses each having a controllable characteristic thereof corresponding to the magnitude of the respective computed answer signal; output multiplexing means forming part of said central station and operable with said signalling means to distribute said output pulses to respective output circuits; a capacitor for each output circuit; each output circuit including means for directing to the associated capacitor a signal derived form the corresponding output pulse signal to control the capacitor charge responsive to the magnitude of said pulse characteristic; an amplifier connected to each capacitor for developing a control signal corresponding to the charge stored in the capacitor without significantly altering the charge level during the periods intervening the received pulses; and output transmission means for sending each control signal to a corresponding operating element of the process.

Claim 20

Apparatus as claimed in claim 12, wherein said output circuit means includes means to alter the charge on each capacitor an amount which is proportional to the controllable characteristic of the corresponding pulse signal.

Claim 21

Apparatus as claimed in claim 13, wherein said signalling means is arranged to produce pulses wherein said controllable characteristic is the time duration of the pulse.

Claim 22

A process control system for setting a number of operating elements such as process valves and the like, said system comprising, in combination: a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; a central station including a digital computer having a computational section operating under program control to process input data supplied thereto; means for directing said measurement signals to said central station; means at said central station to receive said measurement signals and to direct corresponding signals to said computational section of said computer so that the latter can carry out programmed arithmetic operations to produce computed signals; means at said central station to produce electrical output pulses each having a characteristic the magnitude of which corresponds to the magnitude of a respective computed signal; a plurality of output circuits; means to distribute said output pulses to respective output circuits; a plurality of memory devices for said output circuits respectively; circuit means for directing to each memory device a signal derived from the corresponding output pulse signal so as to store in the memory device a signal reflecting the magnitude of a respective operating element of the process; a signal-producing device connected to each memory device for developing a control signal corresponding to the signal stored in the memory device; and means responsive to each control signal to set a corresponding operating element of the process at a level corresponding to the magnitude of the control signal.

Claim 23

A process control system for setting a number of operating elements such as process valves and the like, said system comprising, in combination: a plurality of condition-sensing devices for producing measurement signals representing the magnitudes of respective process variables; a central station including a digital computer having a computational section operating under program control to process input data supplied thereto; means for directing said measurement signals to said central station; means at said central station to receive said measurement signals and to direct corresponding signals to said computational section of said computer so that the latter can carry out programmed arithmetic operations to produce computed signals; means at said central station to produce electrical output pulses each having a characteristic the magnitude of which corresponds to the magnitude of a respective computed signal; a plurality of output circuits; means to distribute said output pulses to respective output circuits; a plurality of memory devices for said output circuits respectively; circuit means for directing to each memory device a signal derived from the corresponding output pulse signal so as to store in the memory device a signal reflecting the magnitude of a respective operating element of the process; a signal-producing device connected to each memory device for developing a control signal corresponding to the signal stored in the memory device; and means responsive to each control signal to set a corresponding operating element of the process at a level corresponding to the magnitude of the control signal.

Claim 24

Apparatus as claimed in claim 15, including switch means operable to condition said system in either digital mode or nondigital mode; signal-generating means for developing adjusting signals independently of said computer; and circuit means operable when said switch means is in nondigital mode to connect said signal-generating means to at least one of said memory devices so as to permit the corresponding adjusting signal to alter the stored signal to any selected level representing a desired magnitude of the corresponding operating element.

Claim 25

Apparatus as claimed in claim 16, wherein said memory device comprises an electrical capacitor for each output circuit.

Claim 26

Apparatus as claimed in claim 17, wherein said signal-generating means comprise manually operable means to produce a charging current for the capacitors to alter the charge levels thereof.

Claim 27

Apparatus as claimed in claim 18, wherein said manually operable means comprises means to selectively produce either a positive or a negative charging current, so as to permit adjusting the operating element in either direction.

Claim 28

Apparatus as claimed in claim 19, wherein said manually operable means includes means to produce currents of at least two significantly different magnitudes, to permit selection of the rate-of-charge of the capacitor charge.

Claim 29

The system of claim 15, wherein said memory device comprises a capacitor and said signal-producing device comprises an amplifier connected to said Capacitor to produce a control signal which is a function of the charge on the associated capacitor.

Claim 30

The system of claim 21, wherein each capacitor is connected in a feedback circuit around the associated amplifier.

Claim 31

The system of claim 21, wherein said output pulse producing means includes switch means operating under the control of said digital computer to direct pulse signals to said capacitor.

Claim 32

In a process control system of the type having a central station including a high-speed digital computer for controlling a plurality of process loops and to which is directed process condition measurement signals for said process loops respectively, the computer including means to perform computations with respect to said measurement signals individually and in sequence so as to develop corresponding digital signals representing instructions for respective process operating elements such as process valves and the like; that improvement in such a system wherein the apparatus further includes; a memory device for each process operating element; an analog signal-producing means connected to each memory device, said signal-producing means serving to produce a control signal the magnitude of which corresponds to the level of the signal stored in the associated memory device; said computer including means operative at time intervals to produce, for each process loop measurement, command signals the magnitude of each of which represents an instruction for setting to a fixed level the operating element for such process loop according to the calculations of the computer at that time; and circuit means responsive to said command signals for storing in each memory device a fixed-magnitude signal having a level responsive to the respective command signal, so that after the command signal has ended the respective operating element will be controlled by the corresponding control signal to a specific fixed setting in accordance with the computer calculations for that operating element.

Claim 33

In a process control system of the type having a central station including a high-speed digital computer for controlling a plurality of process loops and to which is directed process condition measurement signals for said process loops respectively, the computer including means to perform computations with respect to said measurement signals individually and in sequence so as to develop corresponding digital signals representing instructions for respective process operating elements such as process valves and the like; that improvement in such a system wherein the apparatus further includes; a memory device for each process operating element; an analog signal-producing means connected to each memory device, said signal-producing means serving to produce a control signal the magnitude of which corresponds to the level of the signal stored in the associated memory device; said computer including means operative at time intervals to produce, for each process loop measurement, command signals the magnitude of each of which represents an instruction for setting to a fixed level the operating element for such process loop according to the calculations of the computer at that time; and circuit means responsive to said command signals for storing in each memory device a fixed-magnitude signal having a level responsive to the respective command signal, so that after the command signal has ended the respective operating element will be controlled by the corresponding control signal to a specific fixed setting in accordance with the computer calculations for that operating element.

Claim 34

Apparatus as claimed in claim 24, wherein said memory device comprises a capacitor and said signal-producing means comprises an electronic amplifier connected to said capacitor to produce for the respective operating element an output signal corresponding to the charge stored in the capacitor.

Claim 35

Apparatus as claimed in claim 25, including manually operable means for selectively directing to said capacitor positive or negative charging currents for said capacitor, whereby to manually alter the output current so as to adjust the setting of the operating element.

Claim 36

Process control apparatus for controlling the value of a process condition and providing both automatic and nonautomatic modes of functioning, said apparatus comprising: transfer switch means operable into either automatic or nonautomatic state; means to receive at least one measurement signal the magnitude of which corresponds to the measured value of a process condition to be controlled; means responsive to said measurement signal for producing an automatic control signal representing an instruction to a process valve or the like to provide a setting for such valve appropriate to maintaining said process condition at a desired set point value; said responsive means including an electrical amplifier arranged to produce a DC output signal the magnitude of which identifies the setting for the process valve; a capacitor; circuit means operable when said switch means is in automatic state to charge said capacitor to a level corresponding to the magnitude of said DC output signal as determined by said responsive means for controlling the process valve; said capacitor serving when said switch means is in nonautomatic state to maintain the output of said amplifier at a value corresponding to the charge on said capacitor; and manually controllable means operable when said switch means is in nonautomatic state to direct to said capacitor a positive or neGative charging current to controllably alter the charge on said capacitor and thereby alter correspondingly the output signal furnished by said amplifier for controlling the process valve.

Claim 37

Process control apparatus for controlling the value of a process condition and providing both automatic and nonautomatic modes of functioning, said apparatus comprising: transfer switch means operable into either automatic or nonautomatic state; means to receive at least one measurement signal the magnitude of which corresponds to the measured value of a process condition to be controlled; means responsive to said measurement signal for producing an automatic control signal representing an instruction to a process valve or the like to provide a setting for such valve appropriate to maintaining said process condition at a desired set point value; said responsive means including an electrical amplifier arranged to produce a DC output signal the magnitude of which identifies the setting for the process valve; a capacitor; circuit means operable when said switch means is in automatic state to charge said capacitor to a level corresponding to the magnitude of said DC output signal as determined by said responsive means for controlling the process valve; said capacitor serving when said switch means is in nonautomatic state to maintain the output of said amplifier at a value corresponding to the charge on said capacitor; and manually controllable means operable when said switch means is in nonautomatic state to direct to said capacitor a positive or neGative charging current to controllably alter the charge on said capacitor and thereby alter correspondingly the output signal furnished by said amplifier for controlling the process valve.

Claim 38

Apparatus as claimed in claim 27, wherein the charging circuit for said capacitor comprises a series resistor to set the charging current level to a predetermined relatively low level.

Claim 39

apparatus as claimed in claim 27, wherein said capacitor is connected between the output and the input of said amplifier.