Constant range ultrasonic motion detector

• US 4,608,674 A
• Filed: 08/06/1982
• Issued: 08/26/1986
• Est. Priority Date: 08/06/1982
• Status: Expired due to Fees

• Current Assignee: ADT Security Services Incorporated (Apollo Global Management, Inc.)
• Original Assignee: American District Telegraph Company
• Inventors: Guscott, John K.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US06/406,020
• Time in Patent Office: 1,481 Days
• Field of Search: 367/93, 367/94, 340/501
• US Class Current: 367/93
• CPC Class Codes: G08B 13/1627 using Doppler shift detection circuits

Abstract

A constant range ultrasonic motion detector features an ambient atmospheric condition sensor which senses the temperature, pressure, and percent relative humidity of the ambient atmosphere and produces therefrom a range compensation signal to adjust the sensitivity of the ultrasonic motion detector for stabilizing the range. The range compensation signal is applied to adapt detector amplifier gain and/or threshold level to the variation between design and ambient conditions. In one embodiment, an analog summing network at the ambient atmospheric sensor outputs provides the range compensation signal and in a second embodiment a microprocessor is operative to provide the range compensation signal.

Claims

1. An intrusion detection system, comprising:

an ultrasonic motion detector for providing an alarm signal in response to object motion within a range that varies from nominal range with the variation between ambient atmospheric condition and nominal atmospheric condition of the atmospheric sound propagation medium;

an ambient atmospheric condition sensor for providing sensor signals which respectively depend upon at least two distinct ambient atmospheric conditions of the atmospheric sound propagation medium;

means responsive to said sensor signals for combining said sensor signals to provide a range compensation signal which depends on the difference between nominal and ambient atmospheric conditions; and

means for applying said range compensation signal to said ultrasonic motion detector to adapt said effective range to said nominal range.

2. An intrusion detection system, as recited in claim 1, wherein said ultrasonic motion detector includes:

an ultrasonic motion sensor operative to produce an object detect signal in response to said object motion; and

an alarm threshold comparator having an input responsive to said object detect signal and another input responsive to said range compensation signal.

3. An intrusion detection system, as recited in claim 1, wherein said ultrasonic motion detector includes:

an ultrasonic motion sensor including a signal amplifier means operative to provide an object detect signal in response to object motion within said range; and

wherein said range compensation signal is operatively connected to said signal amplifier means to controllably vary the gain of said amplifier means.

4. An intrusion detection system, as recited in claim 2 or 3, wherein said range compensation signal is provided by an analog summing amplifier that weights and adds said sensor signals.

5. An intrusion detection system, as recited in claim 4, wherein said ambient atmospheric condition sensor includes a temperataure sensor, a pressure sensor, and a relative humidity sensor.

6. An intrusion detection system, as recited in claim 2 or 3, wherein said range compensation signal is provided by a digital microprocessor operative in response to said sensor signals to calculate said range compensation signal therefrom.

7. An intrusion detection system, as recited in claim 6, wherein said ambient atmospheric condition sensor includes a temperatuare sensor, a pressure sensor, and a relative humidity sensor.

8. An intrusion detection system, as recited in claim 6, further including memory operatively connected to said digital microprocessor;

wherein said ambient atmospheric sensor has at least two ambient atmospheric condition sensors;

further including at least two comparators, one input of each being respectively connected to a corresponding one of said at least two ambient atmospheric condition sensors, the other input of each being respectively operatively connected to an output port of said digital microprocessor, with the output of each of said comparators being operatively connected to an input of said digital microprocessor;

wherein said microprocessor is operative to read each of said comparators by decrementing a signal at its corresponding output and writing the value therefrom in said memory when the comparator threshold is exceeded to a preselected address location selected to correspond to an associated comparator; and

wherein said microprocessor is operative to read the values from the corresponding addresses in memory and to calculate therefrom said range compensation signal.

22. An ultrasonic intrusion detection system that is substantially free of both false alarms and failure-of-alarm situations, as recited in claim 8, further including memory operatively connected to said digital microprocessor;

wherein said ambient atmospheric sensor has at least two ambient atmospheric condition sensors;

further including at least two comparators, one input of each being respectively connected to a corresponding one of said at least two ambient atmospheric condition sensors, the other input of each being operatively connected to an output of said digital microprocessor, and the output of each of said comparators being operatively connected to an input of the microprocessor;

wherein said microprocessor is operative to read each of said comparators by decrementing a signal at its corresponding output and writing a value therefrom in said memory when the comparator threshold is exceeded to a predetermined address location selected to correspond to an associated comparator; and

wherein said processor is operative to read the values from the corresponding addresses in memory and to calculate said sensor signal by combining the data at the corresponding locations.

9. A range compensated ultrasonic intrusion detection system, comprising:

an ultrasonic motion detector responsive to object motion within the actual range of the ultrasonic motion detector for providing a signal representative of object motion within the actual range;

means responsive to the level of said signal for providing an alarm signal indicating object motion within said range whenever said level exceeds a threshold level selected for a nominal range and noise performance;

an ambient atmospheric sensor responsive to the sound propagation parameters of the ambient atmosphere for providing at least two sensor signals respectively representative of at least two distinct ambient sound propagation parameters; and

means responsive to a predetermined combination of said sensor signals and coupled to said ultrasonic motion detector, for changing at least one of said levels in a first direction if the actual range of said ultrasonic motion detector is less than the nominal range and for changing at least one of said levels in a second direction opposite the first direction if the actual range of the ultrasonic motion detector is greater than the nominal range.

10. A range compensated ultrasonic intrusion detection system, as recited in claim 9, wherein said ambient atmospheric sensor changes said level of said signal representative of object motion in response to the variation between ambient atmospheric condition and nominal atmospheric condition.

11. A range compensated ultrasonic intrusion detection system, as recited in claim 9, wherein said ambient atmospheric sensor changes said threshold level of said level responsive means in response to the variation between ambient atmospheric atmospheric condition and nominal atmospheric condition.

12. A range compensated ultrasonic motion detector, as recited in claim 11, wherein said level responsive means is a threshold comparator.

13. A range compensated ultrasonic intrusion detection system, as recited in claim 10 or 11 wherein said ambient atmospheric sensor includes an ambient temperature, pressure, and relative humidity sensing means coupled to an analog summing network operative to selectively add and weight said signals to provide said levels.

14. A range compensated ultrasonic intrusion detection system as recited in claim 10 or 11 wherein said ambient atmospheric sensor includes an ambient atmospheric temperature, pressure, and relative humidity sensing means operatively connected to a microprocessor operative to provide said levels.

15. An ultrasonic motion detector system that is substantially free of both false alarms and failure-of-alarm situations, comprising:

an ultrasonic motion sensor having a preselected nominal range and an actual range that varies with the sound wave attenuation coefficient of the ambient condition of the atmospheric propagation medium for providing an object detection signal representative of object motion within said actual range;

means including an ambient atmospheric sensor for providing an ambient atmospheric sensor signal representative of a predetermined combination of at least two selected different ambient atmospheric conditions that affect the sound wave attenuation coefficient; and

means coupled to said ultrasonic motion sensor and responsive to said object detection signal and to said ambient atmoshperic sensor signal for providing an alarm signal that indicates object motion within said actual range adapted to said nominal range such that whenever ambient atmospheric conditions produce an actual range that is spatially less extended than nominal range said actual range is effectively extended to said nominal range, and whenever the ambient atmospheric condition produces an actual range that is spatially greater in extent than said nominal range said actual range is effectively contracted to said nominal range thereby substantially eliminating said failure-of-alarm and said false alarm situations, respectively.

16. An ultrasonic motion detection system that is substantially free of both false alarms and a failure-of-alarm situation, as recited in claim 15, wherein said ambient atmospheric sensor includes a temperature sensor for providing a signal representative of the ambient temperature of the atmospheric sound propagation medium.

17. An ultrasonic intrusion detection system that is substantially free of both false alarms and a failure-of-alarm situation, as recited in claim 15, wherein said ambient atmospheric sensor includes a pressure sensor for providing a signal representative of the ambient pressure of the atmospheric sound propagation medium.

18. An ultrasonic intrusion detection system that is substantially free of both false alarms and a failure-of-alarm situation, as recited in claim 15, wherein said ambient atmospheric sensor includes a relative humidity sensor for providing a signal representative of the ambient percent relative humidity of the atmospheric sound propagation medium.

19. An ultrasonic intrusion detection system that is substantially free of both false alarms and a failure-of-alarm situation, as recited in claim 15, 16, 17, or 18, wherein said sensor signal providing means includes an analog summing network and an alarm threshold comparator, said alarm threshold comparator having one input thereof responsive to said object detection signal and another input thereof responsive to the output of said analog summing network so that the level of said comparator is adapted to ambient conditions.

20. An ultrasonic intrusion detection system that is substantially free of both false alarms and a failure-of-alarm situation, as recited in claim 19, wherein said sensor signal providing means includes an analog summing network and an amplifier responsive to said object detection signal, the output signal of said analog summing network being operatively connected to control the gain of said amplifier so that the gain thereof is adapted to ambient conditions.

21. An ultrasonic intrusion detection system that is substantially free of both false alarms and a failure-of-alarm situation, as recited in claim 15, 16, 17, or 18, wherein said alarm signal providing means includes a microprocessor responsive to said ambient atmospheric sensor signal and an alarm threshold comparator, one input of said alarm threshold comparator being responsive to said object detect signal and another input thereof being responsive to the output signal of said microprocessor.