Controller by-pass transfer station for an electron process control servosystem

Claim 2

Electronic process control circuitry comprising: a. controller bypass means connected to a voltage supply terminal and having a circuit output node, said controller bypass means establishing a predetermined voltage difference between said circuit output node and said voltage supply terminal which is equal to the voltage difference across a control element of a process control system through which current flow is to be controlled, and b. means for connecting said circuit output node to a load terminal of said control element whereby the current flowing through said circuit output node is proportional to the voltage difference between said circuit output node and said voltage supply terminal, said voltage difference being adjustable to equal to the voltage drop across said control element so that the current flowing from said load terminal to said output circuit node can be made equal to the current flowing in said control element prior to the connection of said load terminal to said output circuit node whereby a bumpless transfer of a process controller to and from said load terminal may be achieved.

Claim 3

Circuitry defined in claim 1 wherein: a. said controller bypass means includes differential amplifier means coupled to said circuit output mode and including first and second input connections, and b. voltage balance control means coupled to one of said first and second input connections of said differential amplifier means and to said voltage supply terminal for biasing said differential amplifier means with respect to the potential on said voltage supply terminal, so that the voltage difference between said circuit output node and said voltage supply terminal can be adjusted by said balance control means to a value equal to the voltage developed across said control element.

Claim 4

The circuitry defined in claim 2 which further includes current amplifying means connected between said differential amplifier means and said circuit output node for providing a desired predetermined level of current through said circuit output node.

Claim 5

The circuitry defined in claim 3 wherein said current amplifying means includes first and second complementary semiconductor devices connected to said circuit output node, said first semiconductor device providing a source of output current when the controller is drawing more current than the current flowing through said control element, and said second semiconductor device providing a current sink for said control element when the controller current is less than the current through said control element.

Claim 6

The circuitry defined in claim 4 which further includes voltage regulating circuit means connected between said voltage supply terminal and a point of reference potential and providing a plurality of reference potentials for operating said differential amplifier means and biasing same with respect to the potential on said voltage supply terminal.

Claim 7

A process controller bypass subsystem for a closed loop process control servosystem including, in combination: a. a process final control element adapted to function as an electrical-to-mechanical transducer and conducting a predetermined current, the level of which is to be controlled during the removal of an automatic controller from said process control servosystem, and b. a controller bypass transfer station connected to said final control element and operative to be biased by the voltage developed across said final control element for conducting a predictable current therethrough which is approximately equal to the current flowing through said final control element, whereby said transfer station will provide a substitute current path for said final control element when said controller is electrically disconnected from said final control element, said transfer station preventing any undesirable current interruption through said final control element when said automatic controller is removed from said process control system.

Claim 8

A process controller bypass subsystem for a closed loop process control servosystem including, in combination: a. a process final control element adapted to function as an electrical-to-mechanical transducer and conducting a predetermined current, the level of which is to be controlled during the removal of an automatic controller from said process control servosystem, and b. a controller bypass transfer station connected to said final control element and operative to be biased by the voltage developed across said final control element for conducting a predictable current therethrough which is approximately equal to the current flowing through said final control element, whereby said transfer station will provide a substitute current path for said final control element when said controller is electrically disconnected from said final control element, said transfer station preventing any undesirable current interruption through said final control element when said automatic controller is removed from said process control system.

Claim 9

The subsystem defined in claim 6 wherein said transfer station includes a differential amplifier coupled to circuit output node and having at least one input connection thereof operatively biased with respect to the voltage developed across said final control element, so that the output current of said differential amplifier varies in accordance with the current flowing through said final control element.

Claim 10

The subsystem defined in claim 7 wherein said transfer station further includes voltage balance control means connected between said final control element and said input connection of said differential amplifier for biasing said differential amplifier with respect to the potential on one side of said final control element.

Claim 11

The subsystem defined in claim 8 wherein said transfer station further includes: a. a complementary connected current amplifier interconnected between the output of said differential amplifier and said circuit output node for providing a desired level of current through said circuit output node to either source current to or sink current from said circuit output node, depending upon the level of controller current when said automatic controller is connected to said final control element, b. current regulating means including a first reference voltage device connected between said voltage supply terminal and said differential amplifier for providing a first reference operating voltage for said differential amplifier, c. said balance control means including a second reference voltage device connected between said voltage supply terminal and a source of substantially constant current, said second reference voltage device providing a second reference potential, a selected percentage of which is applied to said differential amplifier to thereby enable the conductivity of said differential amplifier to be controlled with respect to the voltage variations across said final control elemEnt, d. a reference buffer amplifier connected between another input connection of said differential amplifier and said balance control means to provide some electrical isolation between said differential amplifier and said balance control means and prevent loading of said balance control means by said differential amplifier, e. said balance control means further including a first voltage divider network connected in parallel with said second reference voltage device and further connected to said one input connection of said differential amplifier for providing a coarse balance control potential for said differential amplifier, and f. said balance control means further including a second voltage divider network connected in parallel with said second reference voltage device and further coupled through said reference buffer amplifier to said another connection of said differential amplifier for providing a fine balance control potential for said amplifier.

Claim 12

The subsystem defined in claim 9 which further includes: a. a null meter connected between said final control element and said circuit output node for measuring the voltage difference between a load terminal of said final control element and said transfer station circuit output node, and b. current limiting means connected between said null meter and said final control elements for limiting the current flowing through said null meter when said null meter is in operation.

Claim 13

Electronic bypass circuitry for enabling a bumpless transfer of a process controller to and from a load terminal in a process control loop, including, in combination: a. an output circuit node, b. means for establishing a predetermined voltage level at said output circuit node equal to the voltage level at said load terminal, and c. means for connecting said load terminal to said output circuit node when said voltage levels at said load terminal and said output circuit code are equal, whereby said circuitry can be adjusted to conduct zero current when connected to said load terminal simultaneously with a process controller and further to conduct process controller current when said process controller is disconnected from said load terminal.

Claim 14

Electronic bypass circuitry for enabling a bumpless transfer of a process controller to and from a load terminal in a process control loop, including, in combination: a. an output circuit node, b. means for establishing a predetermined voltage level at said output circuit node equal to the voltage level at said load terminal, and c. means for connecting said load terminal to said output circuit node when said voltage levels at said load terminal and said output circuit code are equal, whereby said circuitry can be adjusted to conduct zero current when connected to said load terminal simultaneously with a process controller and further to conduct process controller current when said process controller is disconnected from said load terminal.

Claim 15

Circuitry defined in claim 11 wherein: a. said means for establishing a predetermined voltage level includes differential amplifier means connected to a common voltage supply terminal for itself and a final control element of a process control loop, the output of said differential amplifier means being further coupled to said output circuit node, and b. means for switching a null balance meter between said output circuit node and said load terminal for measuring the difference of potential therebetween, whereby said differential amplifier means may be rapidly adjusted to establish equal potential conditions at both said output circuit node and said load terminal.