Event detection system with centralized signal processing and dynamically adjustable detection threshold

• US 5,471,194 A
• Filed: 03/23/1993
• Issued: 11/28/1995
• Est. Priority Date: 03/23/1993
• Status: Expired due to Fees

• Current Assignee: SLC Technologies, Inc. (General Electric Company)
• Original Assignee: Aritech BV
• Inventors: Guscott, John K.
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): Wu, Daniel J.
• Application Number:
  US08/035,978
• Time in Patent Office: 980 Days
• Field of Search: 340/510, 340/511, 340/517, 340/518, 340/522, 340/501
• US Class Current: 340/511
• CPC Class Codes: G08B 29/24 Self-calibration, e.g. compensating for environmental drift or ageing of components

Abstract

An event detection system with centralized signal processing and dynamically adjustable detection threshold includes a number of remotely located event detection units coupled to a single centralized signal processing unit. Each event detection unit provides an event detection signal to the centralized signal processing unit. At least one signal processor in the centralized signal processing unit compares the value of the event detection signal with a dynamically adjustable threshold value, and provides a first detection signal when the event detection signal exceeds the value of the dynamically adjustable threshold. A threshold generator compares the event detection signal and a predetermined offset value, and adjusts the value of the dynamically adjustable threshold as the event detection signal exceeds the offset value. The signal processor then provides a second event detection signal when the event detection signal exceeds the adjusted threshold value. The invention further includes a mutual event verifier located in the centralized signal processing unit, for establishing at least one of the event detection units as a mutual verification event detection unit, and for activating an alarm only upon the concurrence of a detection signal from the designated mutual verification event detection unit, and a second confirming detection signal from any other event detection unit coupled to the system.

Claims

1. An event detection system with centralized signal processing and dynamically adjustable detection threshold, comprising:

a plurality of event detection units, each of said plurality of event detection units including;

at least one event detector, for providing an event signal having a variable value, said event signal indicating the detection of an event; and

a single, centralized signal processing unit, coupled to each of said plurality of event detection units, said centralized signal processing unit including;

at least one event detection signal processor, for processing said event signal, said at least one event detection signal processor including;

a comparator, for comparing the value of said event signal with a dynamically adjustable threshold value having a predetermined initial value, and for providing a first detection signal upon the value of said event signal exceeding the initial value of said dynamically adjustable threshold value;

a threshold generator, responsive to said event signal and to a predetermined offset value, for adjusting the value of said dynamically adjustable threshold, and for providing an adjusted threshold value to said comparator upon the value of said event signal exceeding said predetermined offset value, said adjusted threshold value increasing as a function of increases in value of said event detection voltage signal;

said comparator providing a second, confirming detection signal upon said event signal exceeding the value of said adjusted threshold value; and

alarm apparatus, responsive to said second, confirming detection signal, for providing an indication of a detected and confirmed event;

each of said plurality of event detection units further comprises a current signal source, coupled to said event detector and responsive to said event signal, for providing an event detection current signal; and

said centralized signal processing unit further comprises a plurality of current-to-voltage signal converters, each of said plurality of current-to-voltage signal converters responsive to one of said event detector current signals provided by one of said event detection unites, for converting said event detection current signal to an event detection voltage signal having a corresponding value.

2. The event detection system of claim 1 wherein said at least one event detection signal processor further includes:

at least one alarm timer, responsive to said first detection signal from said comparator, for providing an alarm activation period signal during which an alarm signal may be generated; and

an alarm activator, responsive to said alarm activation period signal and to said second, confirming detection signal, for providing an alarm signal activating said alarm apparatus, for indicating an event has been detected and confirmed.

3. The event detection system of claim 2 wherein said at least one event detection signal processor corresponds to a voltage detection signal processor.

4. The event detection system of claim 1 further including:

a mutual event verifier, responsive to at least one mutual verification event detection unit selector signal, for establishing at least one of said plurality of event detection units as a mutual verification event detection unit, and for activating said alarm apparatus only upon the concurrence of a second, confirming detection signal from said at least one event detection unit established as a mutual verification event detection unit, and a second, confirming detection signal from any other event detection unit coupled to said event detection system.

5. The event detection system of claim 4 wherein said mutual event verifier includes:

a plurality of mutual event occurrence timers, each of said plurality of mutual event occurrence timers responsive to a second, confirming detection signal from an associated event detection unit, and responsive to a mutual verification event detection unit selector signal, for providing a mutual event detection period signal having a predetermined duration, and during which said alarm apparatus may be activated; and

a mutual event detector, coupled to said plurality of mutual event occurrence timers, and responsive to at least one mutual event detection period signal and to said mutual verification event detection unit selector signal, for activating said alarm apparatus upon the concurrence of said mutual event detection period signal generated by an established mutual verification event detection unit and a second, confirming event detection signal from at least any other one of said plurality of event detection units.

6. The event detection system of claim 5 wherein said single centralized signal processor unit further includes:

a mutual event detection unit selector, for providing said mutual verification event detection unit selector signal establishing at least one of said plurality of event detection units as a mutual verification event detection unit.

7. The event detection system of claim 6 wherein said plurality of remotely located event detection units include at least one heat detection unit.

8. The event detection system of claim 6 wherein said plurality of remotely located event detection units include at least one intrusion detection unit.

9. The event detection system of claim 6 wherein said plurality of remotely located event detection units include at least one smoke detection unit.

10. The event detection system of claim 1 wherein each of said plurality of event detection units is a remotely located event detection unit and said single, centralized signal processing unit includes one event detection voltage signal processor for each one of said plurality of remotely located event detection units.

11. The event detection system of claim 1 wherein each of said plurality of event detection units is a remotely located event detection unit and said single centralized signal processing unit detects tampering with any one of said plurality of remotely located event detection units.

12. The event detection system of claim 1 wherein each of said plurality of event detection units is a remotely located event detection unit and said single centralized signal processing unit detects tampering with a cable interconnecting each of said plurality of remotely located event detection units and said single centralized signal processing unit.

13. The event detection system of claim 1 wherein said alarm apparatus provides a visual indication of a detected and confirmed event.

14. The event detection system of claim 1 wherein said alarm apparatus provides an audible indication of a detected and confirmed event.

15. An event detection system with centralized signal processing and dynamically adjustable detection threshold, comprising:

a plurality of remotely located event detection units, each of said plurality of remotely located event detection units including;

at least one event detector, for providing an event signal having a variable value, said event signal indicating the detection of an event; and

a current signal source, coupled to said event detector and responsive to said event signal, for providing an event detection current signal;

a single, centralized signal processing unit, coupled to each of said plurality of remotely located event detection units, said centralized signal processing unit including;

a plurality of current-to-voltage signal converters, each of said plurality of current-to-voltage signal converters responsive to one of said event detector current signals provided by one of said event detection units, for converting said event detection current signal to an event detection voltage signal having a corresponding value; and

at least one event detection voltage signal processor, for processing said event detection voltage signal, said at least one event detection voltage signal processor including;

a comparator, for comparing the value of said event detection voltage signal with a dynamically adjustable threshold value having a predetermined initial value, and for providing a first detection signal upon the value of said event detection voltage signal exceeding the initial value of said dynamically adjustable threshold;

a threshold generator, responsive to said event detection voltage signal and to a predetermined offset value, for adjusting the value of said dynamically adjustable threshold, and for providing an adjusted threshold value to said comparator upon the value of said event detection voltage signal exceeding said predetermined offset value, said adjusted threshold value increasing as a function of increases in value of said event detection voltage signal;

said comparator providing a second, confirming detection signal upon said event detection voltage signal exceeding the value of said adjusted threshold value;

a mutual event detection unit selector, for providing at least one mutual verification event detection unit selector signal establishing at least one of said plurality of event detection units as a mutual verification event detection unit;

a mutual event verifier, responsive to said at least one mutual verification event detection unit selector signal, for providing an alarm activation signal only upon the concurrence of a second, confirming detection signal from said at least one event detection unit established as a mutual verification event detection unit, and a second, confirming detection signal from any other event detection unit coupled to said event detection system; and

alarm apparatus, responsive to said alarm activation signal, for providing an indication of a mutually verified confirmed event.

16. An event detection system with centralized signal processing and dynamically adjustable detection threshold, comprising:

a plurality of remotely located event detection units, each of said plurality of remotely located event detection units including;

at least one event detector, for providing an event signal having a variable value, said event signal indicating the detection of an event; and

a current signal source, coupled to said event detector and responsive to said event signal, for providing an event detection current signal;

a single, centralized signal processing unit, coupled to each of said plurality of remotely located event detection units, said centralized signal processing unit including;

a plurality of current-to-voltage signal converters, each of said plurality of current-to-voltage signal converters responsive to one of said event detector current signals provided by one of said event detection units, for converting said event detection current signal to an event detection voltage signal having a corresponding value; and

at least one event detection voltage signal processor, for processing said event detection voltage signal, said at least one event detection voltage signal processor including;

a comparator, for comparing the value of said event detection voltage signal with a dynamically adjustable threshold value having a predetermined initial value, and for providing a first detection signal upon the value of said event detection voltage signal exceeding the initial value of said dynamically adjustable threshold;

a threshold generator, responsive to said event detection voltage signal and to a predetermined offset value, for adjusting the value of said dynamically adjustable threshold, and for providing an adjusted threshold value to said comparator upon the value of said event detection voltage signal exceeding said predetermined offset value, said adjusted threshold value increasing as a function of increases in value of said event detection voltage signal;

said comparator providing a second, confirming detection signal upon said event detection voltage signal exceeding the value of said adjusted threshold value;

a mutual event detection unit selector, for providing at least one mutual verification event detection unit selector signal establishing at least one of said plurality of event detection units as a mutual verification event detection unit;

a mutual event verifier, responsive to said at least one mutual verification event detection unit selector signal, for providing an alarm activation signal only upon the concurrence of a second, confirming detection signal from said at least one event detection unit established as a mutual verification event detection unit, and a second, confirming detection signal from any other event detection unit coupled to said event detection system;

said mutual event verifier including;

a plurality of mutual event occurrence timers, each of said plurality of mutual event occurrence timers responsive to a second, confirming detection signal from an associated event detection unit, and responsive to a mutual verification event detection unit selector signal, for providing a mutual event detection period signal having a predetermined duration, and during which said alarm apparatus may be activated; and

a mutual event detector, coupled to said plurality of mutual event occurrence timers, and responsive to at least one mutual event detection period signal and to said mutual verification event detection unit selector signal, for providing said alarm activation signal upon the concurrence of said mutual event detection period signal generated by an established mutual verification event detection unit and a second, confirming event detection signal from at least any other one of said plurality of event detection units; and

alarm apparatus, responsive to said alarm activation signal, for providing an indication of a mutually verified event.

17. A method of mutual event verification utilizing an event detection system with centralized signal processing and dynamically adjustable detection threshold, the method comprising:

receiving an event voltage signal having a variable value, said event voltage signal indicating the detection of an event by a remotely located event detection unit;

converting said event voltage signal to an event detection current signal by said remotely located event detection unit;

processing said event detection current signal by a single, centralized signal processor, said processing comprising the steps of;

converting said event detection current signal into an event detection voltage signal having a particular value;

comparing the particular value of said event detection voltage signal with a dynamically adjustable threshold value having a predetermined initial value;

providing a first detection signal upon the value of said event detection voltage signal exceeding the initial value of said dynamically adjustable threshold;

adjusting the value of said dynamically adjustable threshold upon the value of said event detection voltage signal exceeding a predetermined offset value, and for providing an adjusted threshold value;

comparing the event detection voltage signal to the adjusted threshold value;

providing a second, confirming detection signal upon the value of the event detection voltage signal exceeding the value of the adjusted threshold value; and

establishing at least one remotely located event detection unit as a mutual verification event detection unit; and

activating an alarm apparatus only upon the concurrence of a second, confirming detection signal from an established mutual verification event detection unit, and a second, confirming detection signal from any other remotely located event detection unit coupled to the event detection system.