Transmitter with software for determining when to initiate diagnostics

• US 6,119,047 A
• Filed: 11/10/1997
• Issued: 09/12/2000
• Est. Priority Date: 03/28/1996
• Status: Expired due to Term

• Current Assignee: Rosemount Incorporated (Emerson Electric Company)
• Original Assignee: Rosemount Incorporated (Emerson Electric Company)
• Inventors: Warrior, Jogesh, Eryurek, Evren, Esboldt, Steven R.
• Primary Examiner(s): Grant, William
• Assistant Examiner(s): Marc, McDieunel, Marc, McDieunel
• Application Number:
  US08/967,777
• Time in Patent Office: 1,037 Days
• Field of Search: 307/38, 318/601, 280/492.3, 700/28, 700/240, 700/79, 700/51, 700/24, 700/25, 700/109, 700/266, 714/34-41
• US Class Current: 700/28
• CPC Class Codes: G05B 13/0275 using fuzzy logic only
• CPC Class Codes: G05B 21/02 electric
• CPC Class Codes: G05B 23/0221 Preprocessing measurements, e.g. data collection rate adjustment; Standardization of measurements; Time series or signal analysis, e.g. frequency analysis or wavelets; Trustworthiness of measurements; Indexes therefor; Measurements using easily measured parameters to estimate parameters difficult to measure; Virtual sensor creation; De-noising; Sensor fusion; Unconventional preprocessing inherently present in specific fault detection methods like PCA-based methods
• CPC Class Codes: G05B 23/0278 Qualitative, e.g. if-then rules; Fuzzy logic; Lookup tables; Symptomatic search; FMEA

Abstract

A process device couples to a process control loop. The process device receives a process signal. A memory in the process device contains a nominal parameter value. Computing circuitry provides an event output based upon the stored nominal value and the process signal. Output circuitry provides an output in response to the event output.

Claims

1. A process device coupled to a process control loop, comprising:

a process signal input providing a process signal related to a process;

memory containing a nominal parameter value;

computing circuitry providing an event output in response to an event in the process, the evens detected based upon the process signal and the nominal parameter value, the computing circuitry providing the event output when the process has stabilized after initialization; and

output circuitry outputting the event output;

wherein the process control loop is selected from the group consisting of two wire process control loops, three wire process control loops and four wire process control loops.

2. The process device of claim 1 wherein process stabilization is determined by monitoring a process variable.

3. The process device of claim 2 wherein process stabilization is determined by monitoring a rate of change of a statistical parameter of the process variable.

4. The process device of claim 3 wherein the statistical parameter comprises RMS.

5. The process device of claim 3 wherein the statistical parameter comprises standard deviation.

6. The process device of claim 3 wherein process stabilization is determined if the rate of change of the statistical parameter is less than about 2% of a span of the process variable.

7. The process device of claim 1 wherein the device is completely powered with power received from the process control loop.

8. The process device of claim 1 wherein the process signal input comprises a sensor input channel and the process signal comprises a process variable.

9. The process device of claim 8 wherein the process variable is selected from the group consisting of pressure, temperature, pH, flow, turbidity, level, position, conductivity, motor current, motor back emf and vibration.

10. The process device of claim 1 wherein the process signal input comprises a control channel and the process signal comprises a control signal.

11. The process device of claim 1 wherein the process signal input comprises input circuitry coupled to the control loop to receive the process signal from the process control loop.

12. A method in a process device coupled to a process control loop, comprising:

receiving a process signal related to a process;

retrieving a nominal parameter value stored in a memory;

waiting until the process has stabilized after initialization;

detecting an event in the process based upon the process signal and the nominal parameter value when the process has stabilized; and

outputting a signal indicative of the event output;

wherein the process control loop is selected from the group consisting of two wire process control loops, three wire process control loops and four wire process control loops.

13. The method of claim 12 including determining process stabilization by monitoring a process variable.

14. The method of claim 13 wherein process stabilization is determined by monitoring a rate of change of a statistical parameter of the process variable.

15. The method of claim 14 wherein the statistical parameter comprises RMS.

16. The method of claim 14 wherein the statistical parameter comprises standard deviation.

17. The method of claim 14 wherein process stabilization is determined if the rate of change of the statistical parameter is less than about 2% of a span of the process variable.

18. The method of claim 12 including completely powering the device with power received from the process control loop.

19. The method of claim 12 wherein the process signal comprises a process variable.

20. The method of claim 19 wherein the process variable is selected from the group consisting of pressure, temperature, pH, flow, turbidity, level, position, conductivity, motor current, motor back emf and vibration.

21. The method of claim 12 wherein the process signal comprises a control signal.

22. The method of claim 12 wherein the process signal input comprises input circuitry coupled to the control loop to receive the process signal from the process control loop.