Conversion circuit for process control system
First Claim
1. Conversion circuitry for coupling to a field transmitter over a primary process control loop, comprising:
- digital receiver circuitry coupling to the primary loop for receiving a first digital process variable signal and a second digital process variable signal from the primary process control loop and providing a digital output related to the first and second digital process variables;
control circuitry receiving the digital output and responsively providing a secondary loop control output as a function of the first and second digital process variables; and
secondary loop control circuitry for coupling to a secondary process control loop including a current source for controlling current flowing through the secondary loop in response to the secondary loop control output whereby an analog current in the secondary loop is a function of the first digital process variable signal and the second digital process variable provided by the primary process control loop.
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Accused Products
Abstract
Conversion circuitry for use in a process control system is adapted for coupling to a primary process control loop. Digital receiver circuitry in the conversion circuitry receives a digital signal transmitted over the primary process control loop from a field transmitter and responsively provides a digital output. A microprocessor receives the digital output and responsively provides a secondary loop control output. Secondary loop control circuitry for coupling to a secondary process control loop receives the secondary loop control output from the microprocessor and responsively controls current flowing through the secondary process control loop. The current flowing through the secondary process control loop is related to the digital signal transmitted by the field transmitter.
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Citations
46 Claims
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1. Conversion circuitry for coupling to a field transmitter over a primary process control loop, comprising:
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digital receiver circuitry coupling to the primary loop for receiving a first digital process variable signal and a second digital process variable signal from the primary process control loop and providing a digital output related to the first and second digital process variables; control circuitry receiving the digital output and responsively providing a secondary loop control output as a function of the first and second digital process variables; and secondary loop control circuitry for coupling to a secondary process control loop including a current source for controlling current flowing through the secondary loop in response to the secondary loop control output whereby an analog current in the secondary loop is a function of the first digital process variable signal and the second digital process variable provided by the primary process control loop. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. Conversion apparatus adapted to couple to a field transmitter through a primary process control loop, comprising:
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a digital receiver adapted to couple to the primary process control loop having a first process variable signal input, a second process variable signal input and a digital output related to the first and second process variable inputs; a controller having a digital signal input from the digital receiver and having a secondary loop control output as a function of first and second process variable signals; and a secondary loop controller adapted to couple to a secondary process control loop, the loop controller including a current source having an analog current output coupled to the secondary process control loop responsive to the secondary loop control output. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. Conversion circuitry for coupling to a field transmitter over a primary process control loop, comprising:
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means for receiving a first digital process variable signal and a second digital process variable signal from the primary process control loop and providing a digital output related to the first and second digital process variables; means for receiving the digital output and responsively providing a secondary loop control output as a function of the first and second digital process variables; and means for controlling current flowing through the secondary loop in response to the secondary loop control output whereby an analog current in the secondary loop is a function of the first digital process variable signal and the second digital process variable provided by the primary process control loop.
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42. A method of controlling current in a secondary process control loop, comprising:
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receiving a first digital process variable signal and a second digital process variable signal from a primary process control loop; providing a digital output related to the first and second digital process variables; providing a secondary loop control output responsive to the digital output; and controlling analog current in the secondary control loop in response to the secondary loop control output as a function of the first digital process variable signal and the second digital process variable. - View Dependent Claims (43, 44, 45, 46)
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Specification