Introduction to intrusion detection systems
The intrusion detection system detects any attempt to enter the premises, tamper with any system or control devices located in or around the site and all assaults.
A detected alarm shall be immediately received by the alarm management system.
The system shall be capable of being programmed to allow selected alarm initiating devices to set to access mode so that nuisance alarms will not be generated during working hours. The access times must be user select-able so that changes in working hours, days of the week and holiday periods will be accommodated.
Exterior Intrusion Detection Sensors
Exterior intrusion detection sensors detect intruders crossing a particular boundary or entering a protected zone. The sensors can be placed in clear zones e.g. open fields around buildings or along fence lines.Exterior sensors must be resilient enough not only to withstand outdoor weather conditions, such as extreme heat, cold, dust, rain, sleet and snow, but also reliable enough to detect intrusion during such harsh environmental conditions.
Exterior intrusion sensors have a lower probability of detecting intruders and a higher false alarm rate than their interior counterparts. This is due largely to many uncontrollable factors such as wind,rain, ice, standing water, blowing debris, random animals and human activity, as well as other sources to include electronic interference. These factors often require the use of two or more sensors to ensure an effective intrusion detection screen.
The microwave detector has a volumetric detection field and detects movements in a high frequency field. It is shaped with a transmitter and receiver unit.
Most of the units are immune to fluorescent lights, environmental changes and masking but small animals, plants, vehicle movements, watercourses, puddles and rough leaves are often subject to initiate failure alarms.
Active Infrared Beam Sensor
The beam sensor consists of transmitter and receiver. The transmitter will emit the multiply continuous infrared beams to generate an invisible fence between transmitter and receiver, it's active sensors for perimeter detection. Once the intruder breaks multiply beams simultaneously, the alarm will be triggered. The multiply beams triggering theory can ensure the sensor not generating false alarms. Active infrared beam sensors with Rain-splash resistant design, which allow these sensors can be installed outdoor. With AGC control, it can withstand the extremely weather condition like heavy rain, fog, snow...etc.
Buried Line Sensor
The passive sensor system is buried in the ground to detect an intruder. The detection will be by the analysis of changes in stress, strain, seismic energy, pressure or other suitable methods.The sensors must be zoned with a zone length not exceeding 50m.
The active sensor system differs from the passive in the technical principle. Intruder detection will be by analysis of changes in the electromagnetic field between the two cables by using a pair orpairs of ported cables buried in the ground or in concrete or asphalt. One cable is a transmitter and the other a receiver with a maximum zone length of 50m. The signal processing must be immune to slowly changing field characteristics due to seasonal and climatic variations.
External PIR Motion Sensor
The external PIR smart sensor detects a motion of an intruder using a passive infrared detector. The unit should be capable of protecting an open space of 120m², and have a low false alarm rate.The housing must be IP65 rated.
Microwave with PIR Motion Sensor
A microwave with PIR motion sensor combined increases detection accuracy and decreases false alarms.The microwave gives a volumetric, cigar shaped coverage and detects movements in a high frequency field. The combined device alarms when both components, infrared and microwave, are in alarm status during a certain time.
In case of no crossing surveillance, short microwave beams are required to cover the blind area in the proximity of the columns. A slope-free site is required for an immaculate detection.
PIR Motion Sensor
The PIR motion sensor shall provide an alarm to the system control panel whenever an intruder crosses on its beam path. Minimum specification is as follows:
Interior Intrusion Detection Sensors
Interior intrusion detection sensors are used to detect intrusion into a building or facility or a specified area inside a building or facility. Many of these sensors are designed for indoor use only, and should not be exposed to weather elements. Interior sensors perform one of three functions:
- Detection of an intruder approaching or penetrating a secured boundary, such as a door, wall, roof, floor, vent or window
- Detection of an intruder moving within a secured area, such as a room or hallway.
- Detection of an intruder moving, lifting, or touching a particular object.
Interior sensors are also susceptible to false and nuisance alarms, however not to the extent of their exterior counterparts.This is due to the more controlled nature of the environment in which the sensors are employed.
Internal PIR Motion Sensor
Internal PIR smart sensors should be installed on walls or ceilings, with the detection pattern covering the possible intrusion zones. Each detection/surveillance zone can be pictured as a search light beam that gradually widens as the zone extends further from the sensor with different segments being illuminated while others are dark. This design characteristic allows the user to focus the beam on areas where protection is needed while ignoring other areas, such as known sources of false alarms. Tower/ceiling mounted sensors theoretically provide a 360° detection pattern.
The integration of sensors and systems is a major design consideration and is best accomplished as part of an overall system/installation/facility security screen. Although sensors are designed primarily for either interior or exterior applications, many sensors can be used in both environments.
Exterior detection sensors are used to detect unauthorized entry into clear areas or isolation zones that constitute the perimeter of a protected area, a building or a fixed site facility.
Interior detection sensors are used to detect penetration into a structure, movement within a structure or to provide knowledge of intruder contact with a critical or sensitive item.
Magnetic Alarm Contact
A magnetic alarm contact linked to the intruder detection system must be hidden when the door/window is closed. The wiring is to be carried through door frames or hinges and external flexible loops cannot be used. The contact must be a balanced, double reed, wide-gap type. Switches must have integral wiring that is long enough to pass through the door or jamb before connection or joining required. A 10,000,000- cycle life expectancy connected to a 24hr supervised alarm loop is required. All alarms are connected to supervised circuits with end-of-line terminators in parallel and serial.