Two-wire field-mounted process device

• US 6,574,515 B1
• Filed: 05/12/2000
• Issued: 06/03/2003
• Est. Priority Date: 05/12/2000
• Status: Expired due to Term

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Karschnia, Robert J., Peluso, Marcos, Lenz, Gary A., Kirkpatrick, William R., DiMarco, Steven J.
• Primary Examiner(s): PATEL, RAMESH B
• Application Number:
  US09/570,268
• Time in Patent Office: 1,117 Days
• Field of Search: 700/27-30, 700/1-3, 700/11, 700/9, 700/17, 700/37, 700/83, 700/79, 710/105, 710/11, 710/12, 710/16, 710/38, 714/6, 714/11, 370/493, 370/410, 370/437, 370/468
• US Class Current: 700/19
• CPC Class Codes: G05B 19/054 Input/output
• CPC Class Codes: G05B 2219/1127 Selector for I-O, multiplex for I-O
• CPC Class Codes: G05B 2219/1157 I-O used either as input or as output
• CPC Class Codes: G05B 2219/1163 Multiplexer for analog signals
• CPC Class Codes: G05B 2219/14144 Galvanic isolation
• CPC Class Codes: G05B 2219/15091 Power and data bus
• CPC Class Codes: G05B 2219/25188 Superposition high frequency data signal on power lines, current carrier
• CPC Class Codes: G06F 1/182 with special features, e.g. for use in industrial environments; grounding or shielding against radio frequency interference [RFI] or electromagnetical interference [EMI]
• CPC Class Codes: G06F 3/05 Digital input using the sampling of an analogue quantity at regular intervals of time , input from a/d converter or output to d/a converter
• CPC Class Codes: H05K 7/1472 Bus coupling modules, e.g. bus distribution modules
• CPC Class Codes: H05K 7/1484 Electrical diagrams relating to constructional features, e.g. signal routing within PLC; Provisions for disaster recovery, e.g. redundant systems

Abstract

A two-wire field-mounted process device with multiple isolated channels includes a channel that can be an input channel or an output channel. The given input or output channel can couple to multiple sensors or actuators, respectively. The process device is wholly powered by the two-wire process control loop. The process device includes a controller adapted to measure one or more characteristics of sensors coupled to an input channel and to control actuators coupled to an output channel. The controller can be further adapted to execute a user generated control algorithm relating process input information with process output commands. The process device also includes a loop communicator that is adapted to communicate over the two-wire loop.

Claims

1. A two-wire field-mountable process device comprising:

a power module couplable to a two-wire loop and adapted to wholly power the process device with power received from the two-wire loop;

a loop communicator coupled to the power module, and being couplable to the two-wire loop to communicate on the two-wire loop;

a controller coupled to the loop communicator and power module;

a first channel operably coupled to the controller and the power module, the first channel configured to couple to at least a first process interface element through at least a first terminal; and

a second channel operably coupled to the controller and the power module, the second channel being configured to couple to at least a second process interface element through at least a second terminal; and

wherein the first and second channels are substantially electrically isolated from each other and from the power module, loop communicator and controller.

2. The device of claim 1, wherein the first process interface element is a sensor, and the device further includes:

a first multiplexer coupled to the at least first terminal;

a first analog-to-digital converter coupled to the controller and the first multiplexer, the first converter being adapted to convert an analog signal from the at least first terminal, into a digital value and to convey the digital signal to the controller.

3. The device of claim 2, wherein the second process interface element is a sensor, and the device further includes:

a second multiplexer coupled to the at least second terminal;

a second analog-to-digital converter coupled to the controller and the second multiplexer, the second converter being adapted to convert an analog signal from the at least second terminal, into a digital value and to convey the digital signal to the controller.

4. The device of claim 2, wherein the second process interface element provides a digital output, and the process device further includes a second multiplexer coupled to the at least second terminal to receive a plurality of digital inputs and convey signals to the controller based upon at least one of the digital inputs.

5. The device of claim 2, wherein the second process interface element is an actuator, and the process device further includes a second multiplexer coupled to the controller and the at least second terminal to provide a plurality of digital outputs on the at least second terminal based upon a command signal from the controller.

6. The device of claim 3, wherein the controller is adapted to compute a process variable as a function of both signals relative to the first and second process interface elements.

7. The device of claim 1, wherein the first process interface element provides a digital output, and the process device further includes a first multiplexer coupled to the controller and the at least first terminal to receive a plurality of digital inputs and convey signals to the controller based upon at least one of the digital inputs.

8. The device of claim 7, wherein the second process interface element provides a digital output, and the process device further includes a second multiplexer coupled to the controller and the at least second terminal to receive a plurality of digital inputs and convey signals to the controller based upon at least one of the digital inputs.

9. The device of claim 7, wherein the second process interface element is an actuator, and the process device further includes a second multiplexer coupled to the controller and the at least second terminal to provide a plurality of digital outputs on the second plurality of terminals based upon a command signal from the controller.

10. The device of claim 1, wherein the controller is a microprocessor.

11. The device of claim 10, wherein the microprocessor is a low-power microprocessor.

12. The device of claim 10, wherein the microprocessor has a clock speed that is user selectable.

13. The device of claim 1, and further comprising memory coupled to the controller and adapted to store a user-generated control algorithm.

14. The device of claim 13, wherein the control algorithm comprises a sequence of logic conditions.

15. The device of claim 13, wherein the memory is low-power memory.

16. The device of claim 13, wherein the memory is stacked memory.

17. The device of claim 13, wherein the controller is adapted to continuously execute the control algorithm.

18. The device of claim 1, wherein the power module comprises a switching-type power supply.

19. The device of claim 1, wherein the device is housed within an explosion-proof enclosure.

20. The device of claim 1, wherein the power module, loop communicator, controller, first channel, and second channel are intrinsically safe.

21. The device of claim 1 and further comprising a base adapted to mate with a standard size rail.

22. The device of claim 1, wherein the first process interface element is a Resistant Temperature Device (RTD).

23. The device of claim 1, wherein the first and second channels are isolated by optoisolators.

24. A two-wire field-mountable process device comprising:

a power module couplable to a two-wire loop and adapted to wholly power the process device with power received from the two-wire loop;

a loop communicator coupled to the power module, and being couplable to the two-wire loop to communicate on the two-wire loop;

a controller coupled to the loop communicator and power module, and adapted to provide a process variable output based upon at least one process variable;

a memory module coupled to the power module and the controller, the memory module being adapted to store a user-generated control algorithm relating the at least one process variable to the process output; and

an input channel operably coupled to the controller and the power module and electrically isolated from the controller and the power module, the input channel being adapted to receive at least one sensor input; and

wherein the controller computes the process variable based at least in part upon a sensor signal received through the at least one sensor input and the user-generated control algorithm.

25. The device of claim 24, wherein the device is housed within an explosion-proof enclosure.

26. The device of claim 24, wherein the power module, loop communicator, controller, memory module, and input channel are intrinsically safe.

27. The device of claim 24, wherein the user-generated algorithm is expressed as Relay Ladder Logic.

28. The device of claim 24, wherein the user-generated algorithm is expressed as a Sequential Function Chart.

29. The device of claim 24, wherein the memory operates on approximately 3.0 volts.

30. The device of claim 24, wherein the power module is programmable.

31. The device of claim 30, wherein the controller includes a microprocessor having a selectable internal clock rate.

32. The device of claim 24, wherein the controller includes a microprocessor having a selectable internal clock rate.

33. A two-wire field-mountable process device comprising:

a power module couplable to a two-wire loop and adapted to wholly power the process device with power received from the two-wire loop;

a loop communicator coupled to the power module, and being couplable to the two-wire loop to communicate on the two-wire loop;

a controller coupled to the loop communicator and power module, and adapted to provide information relative to at least one process variable;

a memory module coupled to the power module and the controller, the memory module being adapted to store a user-generated control algorithm; and

an output channel operably coupled to the controller and the power module and electrically isolated from the controller and the power module, the output channel being adapted to provide an output based upon a command signal from the controller; and

wherein the controller provides the command signal to the output channel based upon the information and the user-generated algorithm.

34. The device of claim 33, wherein the device is housed within an explosion-proof enclosure.

35. The device of claim 33, wherein the power module, loop communicator, controller, memory module, and output channel are intrinsically safe.

36. The device of claim 33, wherein the user-generated algorithm is expressed as Relay Ladder Logic.

37. The device of claim 33, wherein the user-generated algorithm is expressed as a Sequential Function Chart.

38. The device of claim 33, wherein the memory operates on approximately 3.0 volts.

39. The device of claim 33, wherein the power module is programmable.

40. The device of claim 39, wherein the controller includes a microprocessor having a selectable internal clock rate.

41. The device of claim 33, wherein the controller includes a microprocessor having a selectable internal clock rate.

42. A field-mountable two-wire process device comprising:

means for wholly powering the process device with power received from a two-wire loop;

means for communicating over the two-wire loop;

means for performing input/output; and

means for performing a user-provided control algorithm based at least in part information received from the means for performing input/output.

43. A method in a field-mountable two-wire process device for providing a process variable, the method comprising:

wholly powering the process device with a two-wire loop;

selectively coupling the process device to a first sensor through a first isolated channel to measure a first characteristic of the first sensor;

selectively coupling the process device to a second sensor through a second isolated channel to measure a second characteristic of the second sensor;

computing a process variable based on at least one of the first and second measured characteristics; and

providing a process variable output based on the computed process variable.

44. A method in a field-mountable two-wire process device for providing a process variable, the method comprising:

wholly powering the process device with a two-wire loop;

coupling the process device to at least one sensor to measure at least a first characteristic of the sensor;

computing a process variable output based on operation of an user-generated algorithm and at least the first characteristic; and

providing the process variable output.