30 November 2018
How to choose outdoor sensing technologies
Outdoor protection is becoming increasingly important as it helps detect intruders before they access critical parts of a site. A number of sensing technologies are available providing intelligent triggers to CCTV and intrusion detection systems. They range from passive and active infrared (PIR and AIR) sensors, to intelligent LiDARs, radar, and fibre optic sensors. The most suitable technology choice depends on the site configuration and environment.
Passive infrared sensors (PIRs) capture the thermal electromagnetic waves emitted by all ‘bodies’ that have a temperature. PIRs detect slight temperature changes created by a person or object entering or moving in a secured area. They can be short-range (12m, 15m and up to 24m) providing a volumetric or curtain detection to connect to intrusion detection systems. They can also be long range (30m, 50m up to 100m) and high mount typically connected to a CCTV system, and set so the volumetric detection zone is matching the cameras field of view.
Active infrared technology is well suited to protect perimeter lines, ranging from just a few meters (ideal for protecting a driveway or loading bay) up to 200m with a single pair of beams. Longer distances can be achieved by using a series of beams, protecting larger sites. The way the technology works is simple: one beam (the transmitter) emits an infrared radio signal continuously to another beam (the receiver) which captures the signal using a photodiode, also known as a photoelectric cell. If the beam is broken, it means someone or something has interrupted the signal, and an alarm is generated.
Laser technology also referred to as LiDAR provides an additional level of customisation and built-in analytics. The sensor’s rotating head, or rotating mirror, emits a constant laser beam that scans the area of detection. Each time the beam hits an object, the signal is reflected back to the sensor which then calculates the time it took for the signal to be returned. This is known as ‘Time of Flight’ technology and it enables the sensor to detect the distance, size and speed of moving objects.
Laser sensors offer a wide range of detection angles – 90, 180 and 360 degrees – and detection distance, ranging from a few centimetres up to over 250m. Two-dimensional LiDARs can be installed horizontally, creating a virtual pane that can protect flat roofs, ceilings or the approach to the building. They can also be installed vertically to create a virtual fence or shield to protect building facades.
Lasers and fibre optics
Laser technology can also be used in conjunction with fibre optics to create a powerful intrusion detection sensor directly mounted on to a wall or fence. An alarm processing unit will send a laser pulse over the fibre optics cable and analyse the change in the interference pattern along the cable to determine the kind of disturbance. This enables it to detect if anyone is climbing over, lifting or cutting through the fence. Vibrations caused by the wind, nearby traffic or small animals can be identified and filtered out. It can protect perimeters from less than 100 meters, up to many kilometres.
Radar technology is now being used in commercial security technology. Fixed compact radars allow the monitoring of wide, open areas at distances reaching well over one kilometre.
The radar analyses the reflection of masses, and to differentiate between people from potential nuisance alarms a number of criteria such as direction, speed and movement are analysed. In some radars, built-in analytics will be able to categorise objects such as people, vehicles or even drones.
Using a combination of sensing technologies ensures the deployment of multi-layered protection from the outer perimeter to the building itself. As for any security system, it is key to understand the customer’s requirements and site configuration in order to choose the most appropriate technologies. One size, as they say, rarely if ever fits all!
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Dubai calling: we will be at Intersec
Intersec is a must-attend security event for the Middle East region and beyond, attracting visitors from all over the world. We will be exhibiting our latest products, with our team available to discuss any existing and potential projects.
Enhanced LiDARs on the show
This year we have enhanced our long-range LiDARs series and this will be demonstrated live at the show. The 30m radius RLS-3060L model now features four detection areas that can now be independently adjusted on an analogue connection; and up to eight areas that can be adjusted on an IP connection. The shape of the detection area can also be customised to the layout of the site. An Area Allocation or Masking function will enable users to precisely define a number of independent detection zones. For the advanced RLS-3060-SH model, which is designed to operate in harsher environments, the upgrades enable a Detection Range Expansion mode extending the detection area to 50m radius. When the LiDAR is set up in a vertical detection mode, it can detect a standing or squatting person over 100m making a compelling sensor for perimeter protection.
Our sister company Fiber Sensys will be showcasing their compact Radar range which offers object tracking and object categorising, differentiating between vehicles, people and drones. It complements its fibre optic perimeter fence detection system by offering protection for wide open areas.
Mee the team
A delegation from OPTEX EMEA will be attending the show including our technical engineers, our marketing colleague, Middle East and Africa sales managers, our strategic alliance Manager, and our Managing Director.
If you like to book an appointment please contact us here
Tech tip: How to use the REDWALL SIP View Finder
The Redwall SIP motion sensors provide long range volumetric detection from 30x20m up to 100x3m and trigger CCTV cameras preset in the direction of the area of intrusion. Like any detection equipment, it is key to set and commission the sensor correctly. For this purpose, we advise to use the SIP-AT kit, consisting of the View Finder, the view plates and the walk test unit.
This month’s tech tip focuses on how to use the View Finder effectively, as well as the corresponding plates. Once the Redwall SIP unit is mounted on the wall or a pole, ideally at a height of 4m – or at least above 2.3m, the View Finder should be plugged onto the sensor using the two holes to secure it. The correct viewing plate should be inserted – each SIP model has a corresponding viewing plate.
Looking through the plate, the sensor should be adjusted to ensure that it is grounded at the maximum detection distance. For instance, for a SIP-3020, the sensor should be grounded (not directed towards the sky) at 30m.
Additionally, it is best to avoid having the detection area right at the edge of the security area, rather it is best practice to leave 1m either side. If the detection area is 20m wide, it is better to centre the view at 11m from the edge on either side.
If required, masking sticks can be used to mask part of the detection area.
Watch the installation video here for more information