Process controller with gain-changing circuitry

Claim 2

A multiple-gain process controller having input terminals adapted to be connected to sources of setpoint and process variable signals and an output terminal connected to a controller load circuit, said controller comprising: a. means for generating an error signal based on the difference between the setpoint signal and the process variable signal; b. amplifier means responsive to the error signal for supplying a drive current to the controller load; c. circuit means responsive to the drive current for generating a feedback signal, said circuit means including gain changing means having switching means responsive to a predetermined level of drive current for causing said feedback signal to be in a first proportion to the drive current when the drive current is less than a predetermined level and in a second proportion to the drive current when the drive current is greater than the predetermined level; and d. a feedback circuit connected to the amplifier input and responsive to the feedback signal.

Claim 3

An improved process Controller having automatic gain change at a predetermined controller output level, said process controller including means for generating a setpoint signal and a process variable signal, amplifier means responsive to the difference between the setpoint signal and the process variable signal for supplying a drive current to a controller load, and a negative feedback circuit connected to the input of the amplifier, wherein the improvement comprises: a. first circuit means responsive to the drive current for generating a first signal proportional to said drive current; b. second circuit means for generating a second signal proportional to a predetermined value of the drive current; and c. third circuit means responsive to the first and second signals for introducing a feedback signal to the negative feedback circuit said feedback signal being in a first proportion to the drive current when the first signal is less than the second signal and in a second proportion to the drive current when the first signal is greater than the second signal, said controller having a first gain when the first signal is less than the second signal and a second gain when the first signal is greater than the second signal.

Claim 4

An improved process Controller having automatic gain change at a predetermined controller output level, said process controller including means for generating a setpoint signal and a process variable signal, amplifier means responsive to the difference between the setpoint signal and the process variable signal for supplying a drive current to a controller load, and a negative feedback circuit connected to the input of the amplifier, wherein the improvement comprises: a. first circuit means responsive to the drive current for generating a first signal proportional to said drive current; b. second circuit means for generating a second signal proportional to a predetermined value of the drive current; and c. third circuit means responsive to the first and second signals for introducing a feedback signal to the negative feedback circuit said feedback signal being in a first proportion to the drive current when the first signal is less than the second signal and in a second proportion to the drive current when the first signal is greater than the second signal, said controller having a first gain when the first signal is less than the second signal and a second gain when the first signal is greater than the second signal.

Claim 5

An improved process controller as recited in claim 2 wherein the first circuit means comprises a load sensing resistor in series with the controller load for generating a voltage proportional to the drive current and an amplifier responsive to the voltage across the load sensing resistor for generating the first signal; and wherein the second circuit means comprises a potentiometer connected to a voltage source, the second signal appearing at the arm of the potentiometer.

Claim 6

An improved process controller as recited in claim 3 wherein the third circuit means comprises: a. a pair of resistors serially connected as a voltage divider network, one end of said voltage divider network being driven by the first signal; and b. switching means for automatically connecting the other end of the voltage divider network to the second signal through a very low impedance when the first signal is greater than the second signal and through a very high impedance when the first signal is less than the second signal.

Claim 7

An improved process controller as recited in claim 4 wherein the switching means automatically connects the other end of the voltage divider network to the second signal through a very low impedance when the first signal is less than the second signal and through a very high impedance when the first signal is greater than the second signal.

Claim 8

An improved process controller as recited in claim 4 wherein the switching means comprises a transistor having a base responsive to the second signal, a collector connected to a voltage source and an emitter connected to the other end of the voltage divider network.

Claim 9

An improved process controller as recited in claim 6 wherein the feedback network comprises a proportional capacitor connected between the third signal and the amplifier input.

Claim 10

An improved process controller as recited in claim 7 wherein the feedback network additionally comprises a rate circuit.

Claim 11

An improved process controller as recited in claim 8 wherein the rate circuit comprises a rate resistor in parallel with rate capacitor connected between the amplifier input and the proportional capacitor.