Method of setting a trigger point for an alarm

• US 6,681,194 B2
• Filed: 12/21/2001
• Issued: 01/20/2004
• Est. Priority Date: 12/21/2001
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Doel, David Lacey, Dubay, Ty Brandon
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): LAU, TUNG S
• Application Number:
  US10/036,576
• Publication Number:
  US 20030120452A1
• Time in Patent Office: 760 Days
• Field of Search: 702/127, 342/70, 382/155, 343/5, 328/165, 364/480
• US Class Current: 702/127
• CPC Class Codes: G05B 23/0235 based on a comparison with predetermined threshold or range, e.g. "classical methods", carried out during normal operation; threshold adaptation or choice; when or how to compare with the threshold

Abstract

An approach to setting an alarm limit, which triggers an alarm when a measurement signal reaches the limit. As an example, when a measurement signal is obtained indicating a temperature, the measurement signal can be contaminated with artifacts such noise. The artifacts can falsely indicate that the temperature exceeds a limit, thereby producing false alarms. The invention reduces the number of false alarms, by (1) predicting the likelihood of false alarms for various limits, (2) specifying a desired likelihood, and (3) selecting and using the limit that produces the desired likelihood.

Claims

1. In a process which

(1) monitors a physical parameter,

(2) develops a signal indicating behavior of the physical parameter, and

(3) issues an alert, which is either valid or invalid, when the signal reaches an implemented alert limit,

a method of establishing said implemented alert limit, comprising:

a) estimating the maximum possible number of valid alert limits, MAX, in a time T;

b) finding a test alert limit having the following properties;

i) when applied to simulations of said signal in a simulated time period T, the test alert limit produces a number of invalid alerts N; and

ii) the ratio MAX/N is greater than 0.05; and

c) using the test alert limit which was found as the implemented alert limit.

2. Method according to claim 1, wherein the ratio MAX/N equals 1/20.

3. Method according to claim 1, wherein the ratio MAX/N equals 1/10.

4. Method according to claim 1, wherein the number of valid alerts is known or specified, but not estimated by the simulations.

5. In a process which

(1) monitors a signal, and

(2) issues an alert when the signal reaches a specified alert limit, wherein some alerts are valid and some are invalid,

a method of establishing said specified alert limit, comprising:

a) examining several collections of alerts caused by respective alert limits, by running Monte Carlo computer simulations of the signal;

b) from the several collections, selecting a candidate collection in which the alerts are more than five percent valid; and

c) using the alert limits corresponding to the candidate collection as the specified alert limit.