Interface apparatus for two-wire communication in process control loops
First Claim
1. 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.
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Accused Products
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.
208 Citations
19 Claims
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1. A process control system, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. 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:
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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. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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Specification