These security measures detect movement by sensing pressure placed on them by weight. Two basic forms are normally employed, pressure mats and balanced buried pressure systems. They are usually located where people are mostly likely to step and activate other security measures such as alarms or lights when they measure pressure outside normal parameters.
One of the devices used is a pressure mat. These are simple vinyl mats that a dwelling's occupant places in areas likely to be crossed. As they do not require much installation and no assembly is required, they are among the most inexpensive of security measures.
Design of Pressure Sensor Mats
The mats contain wires encased in vinyl. The wires register weight and then relay signals to the processors. A typical weight threshold that triggers action is twenty-five pounds. Some companies offer a wireless solution for these mats in which the mat sends a radio signal to the processor which then initiates action. The mats often use battery power.
Typically, a battery lasts eight years. Mats usually measure six by eighteen inches or eighteen by twenty-four inches. They may be hidden under rugs or carpets and should be placed in strategic locations, such as by doors or by valuable possessions.
Installation and Operation of Pressure Sensor Mats
Installation of these mats literally entails simply laying them on a floor. They then may simply be hidden under a carpet or rug. When an individual steps on the mat, it sends out a signal to a processor which then relays a command to any of various other systems such as video recorders, lights, an alarm, or other signal.
Balanced Buried Pressure Sensors
Some people opt to detect trespassing by burying sensors underground. The system requires burying pressurized tubes filled with liquid. A processor monitors and regulates the pressure and a valve makes adjustments for changing weather patterns that penetrate underground. When individuals walk over the sensors they exert pressure on the ground which in turn transmits the pressure to the tubes.
The heavier the exertion on the ground, the greater the pressure. For example, a full-grown man exerts more pressure than a child. The processor relays a signal based on the pressure exerted to another system component such as an alarm.
Each system monitors a zone with a maximum radius of 350 feet; however the detection radius is influenced by soil. Experts recommend burying the tubes approximately four feet apart and in most kinds of soil ten inches underground. If you overlay asphalt on the ground your should bury the tubes four to eight inches.
Disadvantages of Pressure Sensor Devices
Like many security measures, these systems also bring disadvantages. One way to deceive the system is to cushion one's steps or to use some means of bridging over the system. However, bridging is only effective on hard surfaces because of softer surfaces allow greater detection range. Although buried pressure systems adjust to most weather conditions, heavy snowfalls may interfere with proper operation.
Likewise, some lay the systems under concrete, but concrete may interfere with the system's ability to register pressure. Tree roots that reach within ten feet of the system may also cause false warnings under windy conditions causing shifts in the soil surrounding the system.
Pressure-sensing security measures ideally may be suited as one component of a more comprehensive system in conjunction with other measures such as other motion detectors, like ultrasound. They are effective in detecting movement over ground, however they may be easily deceived by cushioning steps or bridging over the area of detection if the area is covered with a hard surface such as concrete.