On line monitor for a control device

• US 6,611,724 B1
• Filed: 11/24/1999
• Issued: 08/26/2003
• Est. Priority Date: 11/24/1999
• Status: Expired due to Term

• Current Assignee: Square D Company (Schneider Electric SE)
• Original Assignee: Square D Company (Schneider Electric SE)
• Inventors: Buda, Paul Robert, Winn, Jackie Laverne, Wheaton, Todd Charles, Dew, Larry Alan
• Primary Examiner(s): Voeltz, Emanuel Todd
• Assistant Examiner(s): BARNES-BULLOCK, CRYSTAL JOY
• Application Number:
  US09/448,639
• Time in Patent Office: 1,371 Days
• Field of Search: 700/49, 700/104, 706/908, 706/909, 706/934, 346/14, 367/76
• US Class Current: 700/49
• CPC Class Codes: G05B 19/0428 Safety, monitoring G05B19/0423 takes precedence
• 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

Abstract

An online monitor that can be permanently attached to a device to be monitored continuously monitors a set of analog signals and initiates data capture over a window of time when a user programmable set of conditions is satisfied. The online monitor includes a digital signal processing unit, a modular, interchangeable, analog signal conditioning base unit that can be tailored to the specific requirements of the process to be monitored and a modular, interchangeable, communication interface unit. The interface unit permits the digital signal processing unit to exchange data with external equipment such as network computers via a number of industry standard communication fieldbus protocols. The online monitor provides the capability to define the trigger condition under which data capture is initiated by comparing a user defined signal to a function of the instantaneous value of another signal or constant. Data captured is stored indefinitely in internally battery backed memory and the instant at which data capture is initiated is determined accurately via a time tagging function, so the data can be retrieved at a later time.

Claims

1. A monitoring control device coupled to a system, the monitoring control device comprising:

a Base Unit for receiving a plurality of analog signals from a respective plurality of analog channels and conditioning the received analog signals by a set of predetermined parameters;

a digital signal processor coupled to the Base Unit for receiving the plurality of conditioned analog signals and converting each conditioned analog signal to a respective digital signal, wherein the digital signal processor compares the instantaneous value of each digital signal to a plurality of trigger conditions and initiates a data capture of a subset of data of the analog channels over a time window in response to at least one of the plurality of trigger conditions being satisfied, wherein the identity of the subset corresponds to the identity of the trigger condition;

a non-volatile memory coupled to the digital signal processor for real-time storage of the subset of data captured by the digital signal processor;

a field bus communications adapter coupled to the digital signal processor for providing access to the non-volatile memory wherein the digital signal processor utilizes a command set protocol for providing access to non-volatile memory; and

a field bus network of external devices coupled to the field bus communications adapter for accessing the subset of data stored in the non-volatile memory wherein the field bus network of external devices further provides parameters for defining the plurality of trigger conditions.

2. The monitoring control device of claim 1 wherein the Base Unit comprises a self-contained power supply for generating a plurality of voltage signals for converting the conditioned analog signals to digital signals.

3. The monitoring control device of claim 2, wherein the self-contained power supply derives power from at least one of the plurality of analog channels.

4. The monitoring control device of claim 1, wherein the digital signal processor utilizes a fixed sample rate to convert each conditioned analog signal to the respective digital signal.

5. The monitoring control device of claim 1 wherein the Base Unit and digital signal processor provide a galvanic isolation between the analog signals and the field bus communication adapter.

6. The monitoring control device of claim 1 wherein the parameters for defining the plurality of trigger conditions are stored in the non-volatile memory.

7. The monitoring control device of claim 1 wherein the digital signal processor further comprises an event clock for creating a time stamp identifying a time a trigger condition occurs, wherein the time stamp and the corresponding trigger event is stored in the non-volatile memory.

8. The monitoring control device of claim 7, wherein an external time source synchronizes the event clock at periodic time intervals.

9. The monitoring control device of claim 8, wherein an externally supplied electronic pulse synchronizes the event clock.

10. The monitoring control device of claim 8, wherein the external synchronizing time source is a global positioning system.

11. The monitoring control device of claim 1 wherein the trigger condition comprises a logical comparison of a first parametrically designated analog channel to a time varying threshold derived as a function of a second parametrically designated analog channel.

12. The monitoring control device of claim 11, wherein the time varying threshold function is a percentage of the second parametrically designated analog channel.

13. The monitoring control device of claim 11, wherein the time varying threshold is a fixed constant added to the instantaneous value of the second parametrically designated analog channel.

14. The monitoring control device of claim 1 wherein the trigger condition comprises a logical comparison of an absolute value of a first parametrically designated analog channel to a time varying threshold derived as an absolute value of a function of a second parametrically designated analog channel.

15. The monitoring control device of claim 14, wherein the time varying threshold is derived as the absolute value of a percentage of the second parametrically designated analog channel.

16. The monitoring control device of claims 14, wherein the time varying threshold is derived by adding a fixed constant to the absolute value of a fixed constant added to the instantaneous value of the second parametrically designated analog channel.

17. A method of monitoring control device coupled to a system, the method comprising:

receiving a plurality of analog signals from a respective plurality of analog channels;

conditioning the received analog signals by a set of predetermined parameters;

converting each conditioned analog signal to a respective digital signal;

comparing the instantaneous value of each digital signal to a plurality of trigger conditions wherein a data capture of a subset of data of the analog channels is initiated over a time window in response to at least one of the plurality of trigger conditions being satisfied, wherein the identity of the subset corresponds to the identity of the trigger condition;

storing the subset of data captured in real-time in a non-volatile memory; and

providing access to the non-volatile memory for accessing the subset of data captured and for storing parameters for defining the plurality of trigger conditions wherein a command set protocol is utilized for accessing the non-volatile memory.

18. The method of claim 17, further comprising a step of generating a plurality of voltage signals for converting the conditioned analog signals to the respective digital signal.

19. The method of claim 17, further comprising a step of creating a time stamp identifying a time a trigger occurs.

20. The method of claim 19, further comprising a step of storing the time stamp and the corresponding trigger event in the non-volatile memory.

21. The method of claim 17, wherein the trigger condition comprises a logical comparison of a first analog signal to a time varying threshold derived as a function of a second analog signal.

22. The method of claim 21, wherein the time varying threshold is a percentage of the second analog signal.

23. The method of claim 21, wherein the time varying threshold is a fixed constant added to the instantaneous value of the second analog signal.

24. The method of claim 17, wherein the trigger condition comprises a logical comparison of an absolute value of a first analog signal to a time varying threshold derived as an absolute value of a function of a second analog signal.

25. The method of claim 24, wherein the time varying threshold is derived as the absolute value of a percentage of the second analog signal.

26. The method of claim 24, wherein the time varying threshold is the absolute value of a fixed constant added to the instantaneous value of the second analog signal.