FIELD DEVICE FOR DIGITAL PROCESS CONTROL LOOP DIAGNOSTICS

• US 20090083001A1
• Filed: 09/25/2007
• Published: 03/26/2009
• Est. Priority Date: 09/25/2007
• Status: Active Grant

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Lattimer, Donald R., Huisenga, Garrie D., Lewis, Richard A.
• Granted Patent: US 7,590,511 B2
• Time in Patent Office: Days
• US Class Current: 702/185
• CPC Class Codes: G05B 23/0224 Process history based detection method, e.g. whereby history implies the availability of large amounts of data

Abstract

A diagnostic field device for coupling to a two-wire process control loop of an industrial process control or monitoring system includes digital communication monitoring circuitry which is configured to couple to a two-wire process control loop. The digital communication monitoring circuitry is configured to receive a digital communication signal from the two-wire process control loop. Timing circuitry in the diagnostic field device provides a timing output. Diagnostic circuitry provides a diagnostic output based upon the digital communication signal and the timing output.

Claims

1. A diagnostic field device for coupling to a two-wire process control loop of an industrial process control or monitoring system, comprising;

power supply circuitry configured to coupled to the two-wire process control loop and provide a power output to circuitry of the diagnostic device to thereby power the diagnostic device with power received from the two-wire process control loop;

digital communication monitoring circuitry configured to receive a digital communication signal from the two-wire process control loop;

timing circuitry configured to provide a timing output; and

diagnostic circuitry configured to diagnose operation of the two-wire process control loop based upon the digital communication signal and the timing output.

2. The apparatus of claim 1 including a memory configured to store a diagnostic output from the diagnostic circuitry.

3. The apparatus of claim 1 wherein the digital communication circuitry monitors transmissions from a Link Active Scheduler (LAS) to thereby provide the digital communication signal.

4. The apparatus of claim 1 wherein the diagnostic field device is configured to operate as a transmitter.

5. The apparatus of claim 1 wherein the process control loop operates in accordance with a FieldBus standard.

6. The apparatus of claim 1 wherein the diagnostic circuitry monitors a response time for diagnosing the operation of the two-wire process control loop.

7. The apparatus of claim 6 wherein the response time is related to a failing field device.

8. The apparatus of claim 1 wherein the diagnostic circuitry monitors token hold times.

9. The apparatus of claim 1 wherein the diagnostic circuitry monitors inactive time.

10. The apparatus of claim 1 wherein the diagnostic circuitry monitors a timing of waveforms.

11. The apparatus of claim 1 wherein the diagnostic circuitry monitors slot time violations.

12. The apparatus of claim 1 wherein the diagnostic circuitry monitors stale data indications.

13. The apparatus of claim 1 wherein an intrinsic safety barrier is positioned between the diagnostic field device and a control room.

14. The apparatus of claim 1 wherein the diagnostic circuitry monitors trends in a relationship between the digital communication signal and the timing output.

15. The apparatus of claim 1 wherein the diagnostic circuitry identifies an increase in amplitude of a loop communication waveform.

16. The apparatus of claim 1 wherein the diagnostic circuitry is configured to associate time information with a diagnosed condition of the two-wire process control loop.

17. A method for diagnosing operation of a two-wire process control loop of an industrial process control loop monitoring system, comprising:

receiving power and communication signals from the two-wire process control loop;

powering circuitry of a diagnostic device with power received from the two-wire process control loop;

providing a timing output which is substantially independent of data received from the two-wire process control loop; and

diagnosing operation of the two-wire process control loop based upon a received digital communication signal and the timing output.

18. The method of claim 17 including storing a diagnostic output in a memory.

19. The method of claim 17 wherein the received digital communications signal is from a Link Active Scheduler (LAS).

20. The method of claim 17 wherein the process control loop operates in accordance with a FieldBus standard.

21. The method of claim 17 wherein the diagnosing is based upon a response time.

22. The method of claim 21 wherein the response time is related to a failing field device.

23. The method of claim 17 wherein the diagnosing is based upon token hold times.

24. The method of claim 17 wherein the diagnosing is based upon inactive time.

25. The method of claim 17 wherein the diagnosing is based upon timing of waveforms.

26. The method of claim 17 wherein the diagnosing is based upon slot time violations.

27. The method of claim 17 wherein the diagnosing is based upon stale data indications.

28. The method of claim 17 wherein the diagnosing is based upon trends in a relationship between the digital communication signal and the timing output.

29. The method of claim 17 wherein the diagnosing is based upon identifying an increase in amplitude of a loop communication waveform.

30. The method of claim 17 including associating time information with a diagnosed condition of the two-wire process control loop.