US5434774A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interface apparatus for two-wire communication in process control loops
Assignee: Fisher Controls International LLC
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Filing: 1994-03-02
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Granted: 1995-07-18
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Expires: 2014-03-02
Abstract
Abstract A process control system includes a process controller that develops a controller output signal having at least a desired DC component and an undesired AC component and a device having an adjustable parameter. An interface apparatus is coupled to the process controller and to the device via a two-wire loop, and means are provided for coupling a communication signal onto the two-wire loop between the interface apparatus and the device. The interface apparatus includes means for substantially attenuating the undesired AC component and means electrically coupled to the attenuating means for substantially preventing the communication signal from electrically affecting the process controller. The device is responsive to the DC component of the controller output signal, and the adjustable parameter of the device is responsive to the communication signal.
Inventors
- 👤 Stephen G. Seberger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 22:08
CPC Classifications
G; G05; G05B; G05B15/00; G05B15/02
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
145 words
A process control system, comprising: a process controller that develops a controller output signal having at least a desired DC component; a device having an adjustable parameter adjustable by suitable communication signals from a remote location, said device controllable by the desired DC component of said controller output signal; a control loop, including a two-wire loop; an interface apparatus coupled to the process controller and to the device via said two-wire loop; and means for coupling a communication signal from a remote location onto the two-wire loop between the interface apparatus and the device for adjusting said adjustable parameter; said interface apparatus including enabling means for enabling reliable control of said device by said desired DC component of said controller output signal when the communication signal is present on the two-wire loop and for enabling reliable communication to said device for adjusting said adjustable parameter.
Claim 2
Dependent Claim
145 words
A process control system, comprising: a process controller that develops a controller output signal having at least a desired DC component; a device having an adjustable parameter adjustable by suitable communication signals from a remote location, said device controllable by the desired DC component of said controller output signal; a control loop, including a two-wire loop; an interface apparatus coupled to the process controller and to the device via said two-wire loop; and means for coupling a communication signal from a remote location onto the two-wire loop between the interface apparatus and the device for adjusting said adjustable parameter; said interface apparatus including enabling means for enabling reliable control of said device by said desired DC component of said controller output signal when the communication signal is present on the two-wire loop and for enabling reliable communication to said device for adjusting said adjustable parameter.
Claim 3
Dependent Claim
35 words
The process control system of claim 1, wherein the enabling means includes preventing means for substantially preventing the interface apparatus from so attenuating the communication signal that the communication signal cannot adjust said adjustable parameter.
Claim 4
Dependent Claim
26 words
The process control system of claim 1, wherein the enabling means includes blocking means for substantially preventing the communication signal from electrically affecting the process controller.
Claim 5
Dependent Claim
31 words
The process control system of claim 1, wherein the controller output signal has an undesired AC component, and the enabling means includes attenuating means for substantially attenuating the undesired AC component.
Claim 6
Dependent Claim
49 words
The process control system of claim 4, wherein the enabling means further includes preventing means for substantially preventing the interface apparatus from so attenuating the communication signal that the communication signal cannot adjust said adjustable parameter and for substantially preventing the communication signal from electrically affecting the process controller.
Claim 7
Dependent Claim
37 words
The process control system of claim 5, wherein a voltage drop which is produced across the interface apparatus is small enough to maintain electrical compatibility of the DC component of the controller output signal with the device.
Claim 8
Dependent Claim
21 words
The process control system of claim 5, wherein the enabling means includes an adjustable voltage reference and a high-impedance current source.
Claim 9
Dependent Claim
25 words
The process control system of claim 7, wherein a voltage drop is produced across the interface apparatus, and the voltage drop exceeds about two volts.
Claim 10
Dependent Claim
22 words
The process control system of claim 5, wherein the interface apparatus is powered, at least in part, by the controller output signal.
Claim 11
Dependent Claim
34 words
The process control system of claim 1, further including an intrinsic safety barrier electrically coupled between the interface apparatus and the device wherein the interface apparatus is electrically compatible with the intrinsic safety barrier.
Claim 12
Dependent Claim
127 words
An interface apparatus for use in a process control system for permitting a communication signal to be coupled to a two-wire loop interconnecting a process controller that develops a controller output signal having at least a desired DC component with a device responsive to the desired DC component wherein the device has an adjustable parameter responsive to the communication signal, the interface apparatus comprising: means for coupling the interface apparatus to the two-wire loop; means for coupling the communication signal to the interface apparatus; and enabling means for enabling reliable control of the device by the desired DC component of the controller output signal when the communication signal is present on the two-wire loop and for enabling reliable communication to the device for adjusting the adjustable parameter.
Claim 13
Dependent Claim
127 words
An interface apparatus for use in a process control system for permitting a communication signal to be coupled to a two-wire loop interconnecting a process controller that develops a controller output signal having at least a desired DC component with a device responsive to the desired DC component wherein the device has an adjustable parameter responsive to the communication signal, the interface apparatus comprising: means for coupling the interface apparatus to the two-wire loop; means for coupling the communication signal to the interface apparatus; and enabling means for enabling reliable control of the device by the desired DC component of the controller output signal when the communication signal is present on the two-wire loop and for enabling reliable communication to the device for adjusting the adjustable parameter.
Claim 14
Dependent Claim
34 words
The interface apparatus of claim 11, wherein the enabling means includes preventing means for substantially preventing the interface apparatus from so attenuating the communication signal that the communication signal cannot adjust said adjustable parameter.
Claim 15
Dependent Claim
25 words
The interface apparatus of claim 11, wherein the enabling means includes blocking means for substantially preventing the communication signal from electrically affecting the process controller.
Claim 16
Dependent Claim
35 words
The interface apparatus of claim 11, wherein the controller output signal has an undesired AC component, and the enabling means includes attenuating means for substantially attenuating the undesired AC component of the controller output signal.
Claim 17
Dependent Claim
48 words
The interface apparatus of claim 14, wherein the enabling means further includes preventing means for substantially preventing the interface apparatus from so attenuating the communication signal that the communication signal cannot adjust said adjustable parameter and for substantially preventing the communication signal from electrically affecting the process controller.
Claim 18
Dependent Claim
39 words
The interface apparatus of claim 15, wherein a voltage drop is produced across the interface apparatus, and the voltage drop is small enough to maintain electrical compatibility of the DC component of the controller output signal with the device.
Claim 19
Dependent Claim
20 words
The interface apparatus of claim 15, wherein the enabling means includes an adjustable voltage reference and a high-impedance current source.
Claim 20
Dependent Claim
24 words
The interface apparatus of claim 17, wherein a voltage drop is produced across the interface apparatus, and the voltage drop exceeds about two volts.
Claim 21
Dependent Claim
21 words
The interface apparatus of claim 15, wherein the interface apparatus is powered, at least in part, by the controller output signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-07-17 | 1999-01-16 | 1999-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-07-17 | 2003-01-16 | 2003-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-07-17 | 2007-01-16 | 2007-07-18 | $7700.00 | Window Closed / Lapsed |