“Underground” options for securing the outdoor perimeter / grounds of your client

Let’s take a look at the types of sensors you can bury on the grounds:

1. Passive Magnetic Field Detection
2. E-Field Sensors
3. H-Field Sensors

Let’s look at each on individually:

Passive Magnetic Field Detection

This buried security system is based on the Magnetic Anomaly Detection principle of operation. The system uses an electromagnetic field generator powering with two wires running in parallel. Both wires run along the perimeter and are usually installed about 5 inches apart on top of a wall or about foot buried in the ground. The wires are connected to a signal processor which analyze any change in the magnetic field. This kind of buried security system sensor cable could be buried on the top of almost any kind of wall to provide a regular wall detection ability or be buried in the ground.

Pros: Very low false alarm rate, can be put on top of any wall, very high chance to detect real burglars.

Cons: Can't be installed in near high voltage line or radars and airports.

Conclusion: The best solution in the buried sensors range.

E-Field Sensors

This proximity system can be installed on building perimeters, fences, and walls, and also has the ability to be installed free standing on dedicated poles. The system uses an electromagnetic field generator powering one wire, with another sensing wire running parallel to it. Both wires run along the perimeter and are usually installed about 800 millimetres apart. The sensing wire is connected to a signal processor that analyses:

Amplitude change (mass of intruder),
Rate change (movement of intruder),
Preset disturbance time (time the intruder is in the pattern).

These items define the characteristics of an intruder and when all three are detected simultaneously, an alarm signal is generated. The barrier can provide protection from the ground to about 4 metres of altitude. It is usually configured in zones of about 200 metre lengths depending on the number of sensor wires installed.

Pros: concealed as a buried form.

Cons: expensive, short zones which means more electronic (more money), high rate of false alarms as it might sound as it can define a cat from a human in reality it doesn't work that well as well as extreme weather causes false alarms.

Conclusion: As in the buried security systems field the Passive Magnetic Field Detection will do a better job most of the time.

H-Field Sensors

This system employs an electro-magnetic field disturbance principle based on two unshielded (or ‘leaky’) coaxial cables buried about 10-15cm deep and located at about 2.1 metres apart. The transmitter emits continuous Radio Frequency (RF) energy along one cable and the energy is received by the other cable. When the change in field strength weakens due to the presence of an object and reaches a pre-set lower threshold, an alarm condition is generated. The system is unobtrusive when it has been installed correctly, however care must be taken to ensure the surrounding soil offers good drainage in order to reduce nuisance alarms.

Pros: concealed as a buried form.

Cons: affected by RF noise, high rate of false alarms, hard to install.

Conclusion: Choose one of the other 2 buried security systems sensors.

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Brian K. Allen is a coach, trainer and entrepreneur in Arizona. For
FREE Bodyguard info, goto this site and request the FREE module:
http://www.TheBodyguardCourse.com
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