Near-far security sensor
Described is a security sensor comprising two or more sub-sensors for use in a variety of installations where different magnetic fields may be experienced by the security sensor as a result of the variety of installations. One of the sub-sensors may have a low magnetic sensitivity while the other sub-sensor may have a much higher sensitivity to magnetic fields. In operation, one or both sub-sensors are used to determine if a door or a window has been opened.
1. A near-far security sensor for monitoring a barrier, comprising:
a first sub-sensor for detecting a magnetic field produced by a magnet associated with the barrier;
a second sub-sensor for detecting the magnetic field produced by the magnet associated with the barrier;
a transmitter;
a memory for storing processor-executable instructions; and
a processor coupled to the first sub-sensor, the second sub-sensor, the transmitter and the memory for executing the processor-executable instructions that cause the near-far sensor to:
monitor, by the processor, the first sub-sensor and the second sub-sensor as the barrier is placed into a closed position;
determine, by the processor, that the first sub-sensor has detected the magnetic field and that the second sub-sensor has not detected the magnetic field; and
select, by the processor, the first sub-sensor for monitoring the barrier based on the first sub-sensor detecting the magnetic field.
2. The near-far security sensor of claim 1 , wherein the processor-executable instructions comprise further instructions that causes the near-far security sensor to:
cause, by the processor, the near-far security sensor to enter into a configuration mode of operation from a normal operating mode;
wherein the processor performs the steps of monitoring, determining and selecting after the near-far security sensor is in the configuration mode of operation.
3. The near-far security sensor of claim 1 , wherein the processor-executable instructions comprise further instructions that causes the near-far security sensor to:
ignore, by the processor, signals received from the second sub-sensor.
4. The near-far security sensor of claim 1 , wherein the processor-executable instructions comprise further instructions that cause the near-far sensor to:
periodically monitor, by the processor, the second sub-sensor to determine whether the sensor has been tampered with.
5. The near-far security sensor of claim 4 , wherein the processor-executable instructions comprise further instructions that cause the near-far sensor to:
determine, by the processor, that tampering has occurred when the first sub-sensor does not indicate that the barrier has been moved and when the processor determines that the second sub-sensor detected the presence of a second magnetic field produced by a second magnet.
6. The near-far security sensor of claim 1 , wherein the processor-executable instructions comprise further instructions that cause the near-far sensor to:
determine, by the processor, that the first sub-sensor is first to provide a signal to the processor indicative of the barrier being closed; and
select, by the processor, the first sub-sensor only for monitoring the barrier.
7. The near-far security sensor of claim 1 , wherein the first sub-sensor comprises a reed switch and wherein the processor-executable instructions comprise further instructions that cause the near-far sensor to:
cause, by the processor, the near-far security sensor to enter into a configuration mode of operation from a normal operating mode;
monitor, by the processor, the reed switch and the second sub-sensor as the barrier is placed into a closed and an open position;
determine, by the processor, that both the reed switch and the second sub-sensor detected the magnetic field; and
select, by the processor, the reed switch only for future monitoring by the processor when both the reed switch and the second sub-sensor detected the magnetic field.
8. The near-far security sensor of claim 1 , wherein the first sub-sensor comprises a first magnetic field sensitivity and the second sub-sensor comprises a second magnetic field sensitivity, wherein the second magnetic field sensitivity is at least five times more sensitive than the first magnetic field sensitivity.
9. The near-far security sensor of claim 1 , wherein the first sub-sensor comprises a reed switch and the second sub-sensor comprises a Hall effect sensor.
10. The near-far security sensor of claim 1 , wherein the first sub-sensor comprises a reed switch and the second sub-sensor comprises a magneto resistor.
11. A method performed for monitoring a barrier by a near-far security sensor, comprising:
monitoring the first sub-sensor and the second sub-sensor as the barrier is placed into a closed position;
determining that the first sub-sensor has detected the magnetic field and that the second sub-sensor has not detected the magnetic field; and
selecting the first sub-sensor for monitoring the barrier based on the first sub-sensor detecting the magnetic field.
12. The method of claim 11 , further comprising:
entering into a configuration mode of operation from a normal operating mode;
wherein the steps of monitoring, determining and selecting are performed after the near-far security sensor has entered the configuration mode of operation.
13. The method of claim 11 , further comprising:
ignoring signals received from the second sub-sensor.
14. The method of claim 11 , further comprising:
periodically monitoring the second sub-sensor to determine whether the sensor has been tampered with.
15. The method of claim 14 , further comprising:
determining that tampering has occurred when the first sub-sensor does not indicate that the barrier has been moved and when the processor determines that the second sub-sensor detected the presence of a second magnetic field produced by a second magnet.
16. The method of claim 11 , further comprising:
determining that the first sub-sensor is first to provide a signal to the processor indicative of the barrier being closed; and
selecting the first sub-sensor only for monitoring the barrier.
17. The method of claim 11 , wherein the first sub-sensor comprises a reed switch, further comprising:
causing the near-far security sensor to enter into a configuration mode of operation from a normal operating mode;
monitoring the reed switch and the second sub-sensor as the barrier is placed into a closed and an open position;
determining that both the reed switch and the second sub-sensor detected the magnetic field; and
selecting the reed switch only for future monitoring by the processor when both the reed switch and the second sub-sensor detected the magnetic field.
18. The method of claim 11 , wherein the first sub-sensor comprises a first magnetic field sensitivity and the second sub-sensor comprises a second magnetic field sensitivity, wherein the second magnetic field sensitivity is at least five times more sensitive than the first magnetic field sensitivity.
19. The method of claim 11 , wherein the first sub-sensor comprises a reed switch and the second sub-sensor comprises a Hall effect sensor.
20. The method of claim 11 , wherein the first sub-sensor comprises a reed switch and the second sub-sensor comprises a magneto resistor.