Process control method and apparatus for regulating temperature

Claim 2

A process control method, comprising the steps of: i. generating a fIrst electrical signal representing a measured value of a process variable, ii. generating a second electrical signal representing a desired value of said process variable, iii. generating a third electrical signal, which changes at a prechosen rate corresponding to a desired rate of change of said measured value of said process variable, iv. comparing said second electrical signal with said third electrical signal to generate a fourth electrical signal, v. applying said fourth electrical signal to cause said third electrical signal to change at the prechosen rate towards equality with said second electrical signal, and vi. comparing said first electrical signal with said third electrical signal to produce a process control signal therefrom.

Claim 3

A process control method according to claim 1, including a further step of causing the third electrical signal to have an initial value which is equal to the first electrical signal.

Claim 6

A process control apparatus comprising an electrical circuit having: a means for generating a first electrical signal representing a desired value of a process variable, a means for generating a second electrical signal representing a measured value of said process variable, a first operational amplifier, with an output and a first and second input thereto, said first input being connected to said first signal. a second operational amplifier with an output and a first and a second input thereto, said first input to the second operational amplifier being connected to the second input to the first operational amplifier, a means for generating a third electrical signal, whose value changes at a prechosen rate corresponding to a desired rate of change of said measured value, said means having an input and output, said output being connected to the second input to the first operational amplifier to generate a fourth electrical signal at the output thereof, said fourth electrical signal being applied to the input to the means for generating the third electrical signal, whereby the latter tends towards equality with the first electrical signal, and, means responsive to the output of the second operational amplifier to generate a process control signal.

Claim 7

A process control apparatus comprising an electrical circuit having: a means for generating a first electrical signal representing a desired value of a process variable, a means for generating a second electrical signal representing a measured value of said process variable, a first operational amplifier, with an output and a first and second input thereto, said first input being connected to said first signal. a second operational amplifier with an output and a first and a second input thereto, said first input to the second operational amplifier being connected to the second input to the first operational amplifier, a means for generating a third electrical signal, whose value changes at a prechosen rate corresponding to a desired rate of change of said measured value, said means having an input and output, said output being connected to the second input to the first operational amplifier to generate a fourth electrical signal at the output thereof, said fourth electrical signal being applied to the input to the means for generating the third electrical signal, whereby the latter tends towards equality with the first electrical signal, and, means responsive to the output of the second operational amplifier to generate a process control signal.

Claim 8

Apparatus according to claim 4 including switch means operable to connect the output of said second operational amplifier to the input to the means for generating the third electrical signal, whereby the latter is caused to equal the second electrical signal.

Claim 9

Apparatus according to claim 4 wherein said means for generating the third electrical signal comprises said first operational amplifier and a third operational amplifier having an output and a first and a second input thereto, and a capacitor connected between said output and said first input, the second input being connected to a reference potential, the output of said third operational amplifier being connected to the second input to said first operational amplifier, and the output of the latter amplifier being connected to the first input to the third operational amplifier through a resistor, whereby the eleCtrical charge on said capacitor changes at a prechosen rate determined by the time constant of said resistor and said capacitor, the direction of said change being responsive to the sign of the output of the first operational amplifier.

Claim 10

Apparatus according to claim 5 wherein said means for generating the third electrical signal comprises said first operational amplifier and a third operational amplifier having an output and a first and a second input thereto, and a capacitor connected between said output and said first input, the second input being connected to a reference potential, the output of said third operational amplifier being connected to the second input to said first operational amplifier, and the output of the latter amplifier being connected to the first input to the third operational amplifier through a resistor, whereby the electrical charge on said capacitor changes at a prechosen rate determined by the time constant of said resistor and said capacitor, the direction of said change being responsive to the sign of the output of the first operational amplifier.

Claim 11

A process control apparatus comprising an electrical circuit having: a means for generating a first electrical signal representing a desired value of a process variable, a means for generating a second electrical signal representing a measured value of said process variable, a first operational amplifier, with an output and a first and a second input thereto, said first input being connected to said first signal, a second operational amplifier with an output and a first and second input thereto, said first input to the second operational amplifier being connected to the second input to the first operational amplifier, a third operational amplifier having an output and a first and second input thereto, and a capacitor connected between said output and said first input, the second input being connected to a reference potential, the output of said third operational amplifier being connected to the second input to said first operational amplifier, and the output of the latter amplifier being connected to the first input to the third operational amplifier through a resistor whereby a third electrical signal whose value changes at a prechosen rate corresponding to a desired rate of change of said measured value is generated at the output of said third operational amplifier, said third electrical signal tending towards equality with the first electrical signal, means responsive to the output of said second operational amplifier to generate a process control signal, and switch means operable to connect the output of said second operational amplifier to the first input to the third operational amplifier, whereby the third electrical signal is caused to equal the second electrical signal.

Claim 12

A process control apparatus comprising an electrical circuit having: a means for generating a first electrical signal representing a desired value of a process variable, a means for generating a second electrical signal representing a measured value of said process variable, a first operational amplifier, with an output and a first and a second input thereto, said first input being connected to said first signal, a second operational amplifier with an output and a first and second input thereto, said first input to the second operational amplifier being connected to the second input to the first operational amplifier, a third operational amplifier having an output and a first and second input thereto, and a capacitor connected between said output and said first input, the second input being connected to a reference potential, the output of said third operational amplifier being connected to the second input to said first operational amplifier, and the output of the latter amplifier being connected to the first input to the third operational amplifier through a resistor whereby a third electrical signal whose value changes at a prechosen rate corresponding to a desired rate of change of said measured value is generated at the output of said third operational amplifier, said third electrical signal tending towards equality with the first electrical signal, means responsive to the output of said second operational amplifier to generate a process control signal, and switch means operable to connect the output of said second operational amplifier to the first input to the third operational amplifier, whereby the third electrical signal is caused to equal the second electrical signal.

Claim 13

A process control apparatus according to claim 8, including a plurality of resistors and associated switch means whereby the output of the first operational amplifier is selectively connectable through the resistors by the associated switch means to the first input of the third operational amplifier, so that the rate of change of the third electrical signal corresponding to a desired rate of change of said measured value may be pre-selected.

Claim 14

A process control apparatus according to claim 9, wherein the means responsive to the output of the second operational amplifier is a polarized relay.

Claim 15

A process control apparatus according to claim 8 including a fourth operational amplifier with an output and a first and second input thereto, and a capacitor and a resistor connected in series between said output and said first input, said first input being connected to the output of the third operational amplifier, and said second input to the fourth operational amplifier being connected to the second electrical signal, whereby the fourth operational amplifier generates a signal whose magnitude is proportional to the difference between the second and third electrical signals,

Claim 16

A process control apparatus according to claim 9 including a fourth operational amplifier with an output and a first and second input thereto, and a capacitor and resistor connected in series between said output and said first input, said first input being connected to the output of the third operational amplifier, and said second input to the fourth operational amplifier being connected to the second electrical signal, whereby the fourth operational amplifier generates a signal whose magnitude is proportional to the difference between the second and third electrical signals.

Claim 17

A process control apparatus according to claim 9 for controlling temperature in a process wherein the means for generating the first electrical signal includes a thermocouple device.

Claim 18

A process control apparatus according to claim 9 wherein the means for generating the first electrical signal includes a resistance thermometer.

Claim 19

A temperature control apparatus comprising an electrical circuit having: a means for generating a first electrical signal representing a desired value of the variable temperature, a means for generating a second electrical signal representing a measured value of said temperature, a first operational amplifier, with an output and a first and a second input thereto, said first input being connected to said first signal, a second operational amplifier with an output and a first and a second input thereto, said first input to the second operational amplifier being connected to the second input to the first operational amplifier, a means for generating a third electrical signal, whose value changes at a prechosen rate corresponding to a desired rate of change of said measured value, said means having an input and output, said output being connected to the second input to the first operational amplifier to generate a fourth electrical signal at the output thereof, said fourth electrical signal being applied to the input to the means for generating the third electrical signal, whereby the latter tends towards equality with the first electrical signal, and, means responsive to the output of the second operational amplifier to generate a temperature control signal.

Claim 20

A temperature control apparatus comprising an electrical circuit having: a means for generating a first electrical signal representing a desired value of the variable temperature, a means for generating a second electrical signal representing a measured value of said temperature, a first operational amplifier, with an output and a first and a second input thereto, said first input being connected to said first signal, a second operational amplifier with an output and a first and a second input thereto, said first input to the second operational amplifier being connected to the second input to the first operational amplifier, a means for generating a third electrical signal, whose value changes at a prechosen rate corresponding to a desired rate of change of said measured value, said means having an input and output, said output being connected to the second input to the first operational amplifier to generate a fourth electrical signal at the output thereof, said fourth electrical signal being applied to the input to the means for generating the third electrical signal, whereby the latter tends towards equality with the first electrical signal, and, means responsive to the output of the second operational amplifier to generate a temperature control signal.