Common-Mode Noise Reduction Circuit
First Claim
9. A method of operating a field device in a process control network, wherein the field device communicates with a remote device via a first wired communication link and with a process control network via a second wired communication link, and wherein the first wired communication link has a plurality of wires connected to the field device via a plurality of respective inputs, the method comprising:
- obtaining a first input impedance to a signal on a first one of the plurality of wires at a first one of the plurality of inputs;
obtaining a second input impedance to a signal on a second one of the plurality of wires at a second one of the plurality of inputs; and
adjusting the second input impedance to match the first input impedance in order to reduce common-mode noise on the first communication link.
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Accused Products
Abstract
A system operating in a process control environment includes a field device to perform a process control function in the process control environment, a remote device disposed away from the field device to perform an auxiliary function associated with the process control function of the field device, a first wired communication link communicatively coupled to the field device and to the remote device to support data communication between the field device and the remote device, and a common-mode noise reduction circuit coupled to the field device and to the wired communication link to reduce common-mode noise generated in the first wired communication link.
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Citations
24 Claims
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9. A method of operating a field device in a process control network, wherein the field device communicates with a remote device via a first wired communication link and with a process control network via a second wired communication link, and wherein the first wired communication link has a plurality of wires connected to the field device via a plurality of respective inputs, the method comprising:
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obtaining a first input impedance to a signal on a first one of the plurality of wires at a first one of the plurality of inputs; obtaining a second input impedance to a signal on a second one of the plurality of wires at a second one of the plurality of inputs; and adjusting the second input impedance to match the first input impedance in order to reduce common-mode noise on the first communication link. - View Dependent Claims (10, 11)
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12. A field device for use in a network operating in a process control environment, comprising:
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an operational unit to perform a physical step in the process control environment; a first interface coupled to a first communication link to communicate with a remote device; a second interface coupled to a second communication link to communicate process control information to the network; and a common-mode noise reduction circuit coupled to the first interface to reduce common-mode noise generated in the first communication link. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A noise-reduction circuit for use with a device coupled to a wired communication link, wherein the device includes a plurality of inputs to connect to a plurality of wires of the wired communication link, the noise-reduction circuit comprising:
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a first circuit input coupled to a first one of the plurality of wires at a first one of the plurality of inputs; a second circuit input coupled to a second one of the plurality of wires at a second one of the plurality of inputs; an impedance matching unit to match an input AC impedance associated with the second one of the plurality of inputs to an input AC impedance associated with the first one of the plurality of inputs, and to provide matching input AC impedances at the first one of the plurality of inputs and at the second one of the plurality of inputs. - View Dependent Claims (1, 2, 3, 4, 5, 6, 7, 8, 20, 21, 22, 23)
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21-1. The noise-reduction circuit of claim 20, wherein the impedance matching unit further comprises a resistor connected in series between the output and the second circuit input to approximately match impedance on the first one of the plurality of wires.
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24. A system operating in a process control environment, the system comprising:
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a field device to perform a process control function in the process control environment; a remote device disposed away from the field device to perform an auxiliary function associated with the process control function of the field device; a first wired communication link communicatively coupled to the field device and to the remote device to support data communication between the field device and the remote device, wherein the first wired communication link includes; a first electrical wire associated with a first impedance; and a second electrical wire associated with a second impedance; and a noise reduction circuit coupled to the field device and to the wired communication link, including; an input contact coupled to the first electrical wire to sense the first impedance; an output contact coupled to the second electrical wire; and an impedance matching component operatively coupled to the input contact and to the output contact;
wherein the second impedance is approximately equal to the first impedance during operation of the noise reduction circuit.
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Specification