Singular housing window or door intrusion detector using earth magnetic field sensor

• US 6,472,993 B1
• Filed: 10/16/2001
• Issued: 10/29/2002
• Est. Priority Date: 10/16/2001
• Status: Expired due to Term

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Pittway Corporation (Honeywell International Inc.)
• Inventors: Addy, Kenneth L.
• Primary Examiner(s): Wu, Daniel J.
• Assistant Examiner(s): Nguyen, Tai T.
• Application Number:
  US09/982,357
• Time in Patent Office: 378 Days
• Field of Search: 340/686.1, 340/545.1, 340/545.6, 340/545.9, 340/547, 340/539, 340/693.9, 340/568.1, 340/571, 340/689
• US Class Current: 340/686.1
• CPC Class Codes: G08B 13/08 by opening, e.g. of door, of window, of drawer, of shutter, of curtain, of blind
• CPC Class Codes: G08B 13/2491 Intrusion detection systems, i.e. where the body of an intruder causes the interference with the electromagnetic field

Abstract

The present invention is a method, an apparatus, and a system for detecting a change in position of a door or a window in an alarm system. The present invention is a singular housing with a magnetometer for monitoring the magnetic field of the earth, and a microprocessor for detecting a change in the position of the singular housing with respect to the magnetic field of the earth. The microprocessor generates an alarm signal upon detecting the change, and causes the alarm signal to be transmitted, by wireless transmission, to a remote receiving station.

Claims

1. A method of detecting a change in position of an entrance closure in an alarm system comprising the steps of:

a) attaching a singular housing on the entrance closure that is being monitored;

b) monitoring, with apparatus in the housing, the magnetic field of the earth;

c) detecting, with apparatus in the housing, a change in the position of the housing with respect to the magnetic field of the earth;

d) generating an alarm signal upon detecting a change in position of the housing with respect to the magnetic field of the earth that exceeds a first predetermined threshold;

e) transmitting by wireless transmission the alarm signal to a remote receiving station; and

f) generating a trouble signal upon detecting a change in position of the housing with respect to the magnetic field of the earth that exceeds a second predetermined threshold.

2. The method of claim 1 wherein the entrance enclosure is a door.

3. The method of claim 1 wherein the entrance enclosure is a window.

4. The method of claim 1 wherein said apparatus in the housing comprises:

a) a magnetometer that detects the earth'"'"'s magnetic field and generates an output signal, wherein the output signal is correlated to the earth'"'"'s magnetic field;

b) a microprocessor for detecting a change in the output signal from the magnetometer, and for generating an alarm signal when the change is greater than the first predetermined threshold; and

c) an RF transmitter for transmitting the alarm signal.

5. The method of claim 4 wherein said monitoring step comprises the steps of:

a) determining a static output signal from the magnetometer;

b) storing the static output signal from the magnetometer; and

c) sampling the output signal from the magnetometer at a predetermined time interval.

6. The method of claim 4 wherein said detecting step comprises the steps of:

a) subtracting the sampled output from the magnetometer from the stored static output of the magnetometer to produce a difference value; and

b) determining if the absolute value of the difference value is greater than the first predetermined value.

7. The method of claim 1 wherein said step of detecting a change in the position of the housing with respect to the magnetic field of the earth takes place on three axis.

8. The method of claim 7 wherein said step of generating an alarm signal occurs upon detecting a change in position of the housing in two of the three axes.

9. The method of claim 1 wherein the remote receiving station correlates the alarm signal with a second alarm signal from a second sensor.

10. The method of claim 1 wherein the second predetermined threshold is less than the first predetermined threshold.

11. An apparatus for detecting a change in position of an entrance closure in an alarm system comprising:

a singular housing attached to an entrance closure being monitored;

the housing comprising;

a) means for monitoring the magnetic field of the earth;

b) means for detecting a change in the position of the housing with respect to the magnetic field of the earth;

c) means for generating an alarm signal upon detecting a change in position of the housing with respect to the magnetic field of the earth that exceeds a first predetermined threshold;

d) means for transmitting by wireless transmission the alarm signal to a remote receiving station; and

e) means for generating a trouble signal upon detecting a change in position of the housing with respect to the magnetic field of the earth that exceeds a second predetermined threshold.

12. The apparatus of claim 11 wherein the entrance enclosure is a door.

13. The apparatus of claim 11, wherein the entrance enclosure is a window.

14. The apparatus of claim 11 wherein said means for monitoring comprises:

a) a magnetometer that detects the earth'"'"'s magnetic field and generates an output signal, wherein the output signal is correlated to the earth'"'"'s magnetic field; and

b) a microprocessor for sampling the output signal and evaluating it.

15. The apparatus of claim 11 wherein said apparatus for detecting a change in the position of the housing with respect to the magnetic field of the earth takes place on three axes.

16. The apparatus of claim 15 wherein said means for generating an alarm signal generates an alarm signal upon the detection of a change in position of the housing in two of the three axes.

17. The apparatus of claim 11 wherein the remote receiving station correlates the alarm signal with a second alarm signal from a second sensor.

18. The apparatus of claim 11 wherein the alarm signal contains a unique transmitter identification number.

19. An alarm system comprising:

a) an apparatus for detecting a change in position of an entrance closure comprising;

i. a singular housing attached to the entrance closure being monitored;

the housing comprising;

1. means for monitoring the magnetic field of the earth;

2. means for detecting a change in the position of the housing with respect to the magnetic field of the earth;

3. means for generating an alarm signal upon detecting a change in position of the housing with respect to the magnetic field of the earth that exceeds a first predetermined threshold;

4. means for transmitting by wireless transmission the alarm signal to a remote receiving station; and

5. means for generating a trouble signal upon detecting a change in position of the housing with respect to the magnetic field of the earth that exceeds a second predetermined threshold; and

b) a receiving station located remotely from the housing comprising

i. means for receiving by wireless transmission the alarm signal from the housing, and

ii. means for indicating an alarm condition in response to receipt of the receipt of the alarm signal.