US3696304A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Proportional only process controller
Assignee: Monsanto Co
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Filing: 1970-06-29
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Granted: 1972-10-03
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Expires: 1990-06-29
Abstract
Abstract Automatic process controller circuitry for producing an output current which is proportional to a process variable input signal. A differential operational amplifier is connected to receive set point and process variable input signals and provides an output voltage which is proportional to the difference between these two signals. An adjustable proportional band series output impedance is connected between the output of the operational amplifier and a controller circuit output node, and this series impedance converts the output voltage of said amplifier to a current. The voltage developed across this variable series output impedance is differentially fed back via positive and negative feedback loops to the inverting and noninverting inputs of the operational amplifier, and such feedback connection enables the proportional current flowing through the variable series output impedance to be made constant and independent of the output voltage of the operational amplifier. Also, since the load current flowing in the transducer driven by the above controller circuitry can be made equal or proportional to this proportional current, said load current can be adjusted to a value wholly independent of the internal resistance of the driven transducer.
Inventors
- 👤 Louis H Fricke Jr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 03:11
CPC Classifications
G; G05; G05B; G05B11/00; G05B11/01; G05B11/36; G06; G06G; G06G7/00; G06G7/10; H; H03; H03F; H03F3/00; H03F3/34; H03F3/343
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
233 words
A process controller for producing an output current proportional to changes in a process variable input signal applied thereto, including in combination: a. input circuit means for receiving process variable and set point input signals, b. differential amplifier means having first and second input terminals thereof connected to said input circuit means for differentially receiving and amplifying said process variable and set point input signals, c. a series output resistance connected between an output terminal of said differential amplifier means and an output circuit node, d. a first conductive feedback path connected to one point on said output resistance and between said output terminal of saiD differential amplifier means and said first input terminal thereof, and e. a second conductive feedback path connected between another point on said series output resistance and said second input terminal of said differential amplifier means, so that the voltage differentially fed back to said first and second input terminals of said differential amplifier means is that voltage developed between said first and second points on said series output resistance, whereby the proportional output current flowing through said series output resistance and through said output circuit node is independent of the internal impedance of the transducer connected to said output circuit node and driven by said controller, and is further independent of the absolute value of the output voltage at said output terminal of said differential amplifier means.
Claim 2
Dependent Claim
233 words
A process controller for producing an output current proportional to changes in a process variable input signal applied thereto, including in combination: a. input circuit means for receiving process variable and set point input signals, b. differential amplifier means having first and second input terminals thereof connected to said input circuit means for differentially receiving and amplifying said process variable and set point input signals, c. a series output resistance connected between an output terminal of said differential amplifier means and an output circuit node, d. a first conductive feedback path connected to one point on said output resistance and between said output terminal of saiD differential amplifier means and said first input terminal thereof, and e. a second conductive feedback path connected between another point on said series output resistance and said second input terminal of said differential amplifier means, so that the voltage differentially fed back to said first and second input terminals of said differential amplifier means is that voltage developed between said first and second points on said series output resistance, whereby the proportional output current flowing through said series output resistance and through said output circuit node is independent of the internal impedance of the transducer connected to said output circuit node and driven by said controller, and is further independent of the absolute value of the output voltage at said output terminal of said differential amplifier means.
Claim 3
Dependent Claim
175 words
The controller defined in claim 1 wherein: a. said first conductive path includes a first feed-back resistor connected between said output terminal of said differential amplifier means and said first input terminal thereof, b. said second conductive feedback path includes a second feedback resistor connected between said circuit output node and said second input terminal of said differential amplifier means, said input circuit means further includes, c. a first input resistor connected between a set point input terminal and said first input terminal of said differential amplifier means, and d. a second input resistor connected between a process variable input terminal and said second input terminal of said differential amplifier means, whereby said first and second input terminals of said differential amplifier means serve as first and second summing junctions, respectively, for said set point and process variable input signals, and the ratio of said first input resistor to said first feedback resistor and the ratio of said second input resistor to said second feedback resistor establishes the proportional band current range of said controller.
Claim 4
Dependent Claim
48 words
The controller defined in claim 2 wherein said series output impedance includes a fixed resistor portion and a variable resistor portion, so that current flowing through said series output impedance may be varied in accordance with the desired proportional band output current flowing into said circuit output node.
Claim 5
Dependent Claim
80 words
The controller defined in claim 1 which further includes an adjustable constant current source connected between said circuit output node and a point of reference potential, said constant current source conducting a current approximately equal to the difference between the current flowing into said circuit output node and the current flowing through said series output resistance to thereby permit adjustment of the output D.C. bias current flowing into said output circuit node from the stage driven thereat by said controller.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-10-03 | 1976-04-03 | 1976-10-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-03 | 1980-04-03 | 1980-10-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-03 | 1984-04-03 | 1984-10-03 | $7700.00 | Window Closed / Lapsed |