March 26, 2017

How to Install the Fence Sensor

SAT Patrol Perimeter Protection System

 

Installation Manual

An Introduction to the SAT Patrol Perimeter Security System.

SAT Patrol is a highly efficient perimeter intruder detection system, designed for use on virtually all types of fence. It has been successfully deployed on chain link (both galvanized and plastic coated), all types of welded mesh, expanded mesh and most types of palisade fences. In addition, it can be used to protect the walls and roofing of buildings. There are two key components to the SAT Patrol perimeter intrusion detection system. The first is a special microphonic sensor cable, which is attached to the fabric being protected. The cable has the effect of converting the fence or roof etc into a giant high fidelity microphone, which will “listen” for any intrusion attempts. The electrical output of the cable is a faithful reproduction of all of the noises generated by the fence. The cable is tough, long lasting, easy to install and unobtrusive. The sensor cable may be attached directly to the fence with standard black plastic cable ties, using a tie wrap gun to minimize installation time. Alternatively, if additional mechanical protection is required for the cable, it can be installed in a plastic or metal conduit. The sensor cable is totally passive and is available in a range of sensitivities to suit the specific application. The second key component of the SAT Patrol system is the electronic Analyzer, a signal processor which continuously monitors the output of the sensor cable. It is designed to ignore the signals generated by environmental effects, such as wind, rain, birds etc, but detect any attempt at breaching the perimeter fence by, for example, climb over, cut through or jacking. The Analyzer uses the latest microprocessor technology and is housed in a robust, fully weatherproof diecast metal box. The Analyzer continuously checks the integrity of the sensor cable by monitoring a termination resistor which is attached to the outer end of the sensor cable. If the cable is cut, damaged or in any way interfered with, the Analyzer detects this and signals it as a tamper alarm condition.

SAT Patrol is rapidly installed and is easy to set up. It can be used for both permanent and temporary installations and is designed to interface to a conventional intruder alarm panel. However, it has the added operational advantage of an audio output. If an alarm is generated, the person responding to the alarm can “listen in” to the fence and confirm that an intrusion is taking place. This facility is available on every SAT Patrol installation, provided the necessary (two wire) connection is installed between the Analyzer and central monitoring station. For installing the SAT Patrol system on gates, a bypass switch unit is available. This enables a section of sensor cable, installed on an entrance gate in the fence, to be switched out. The gate can then be opened and closed without the need to disable the SAT Patrol system on the remainder of the zone. The bypass switch can either be operated at the gate location with a key, or it can be supplied with a relay to enable remote operation from the control center.

Properly installed, SAT Patrol provides a cost effective and highly reliable fence protection system, with a high probability of detecting an intruder combined with a low nuisance or false alarm rate.

Figu

re 1

A SAT Patrol system installed on a chain link fence

 

 

The Site Survey

The key to the successful installation of any security system is planning, and SAT Patrol is no exception. Time spent on the site survey will pay dividends during the installation and commissioning phases of the system. It will also help to eliminate the need to return to the site after the hand-over to track down the cause of problems such as false alarms.

The condition of the fence

First of all, examine the fence itself and decide whether the site security will actually be improved by the installation of an intrusion detection system. If the fence will not physically prevent an average person climbing over it, or the fabric and/or the support posts are worn or damaged, a security system attached to the fence is unlikely to increase the security of the site. SAT Patrol should only be attached to fences of sound construction and adequate height, say a minimum of 7 feet. The installation of SAT Patrol should never be used as a substitute for the replacement of an inadequate or worn out fence. Walk around the entire perimeter, taking a careful look at the fence and noting any places which require repair or maintenance. This inspection is to identify sources of extraneous noise, which will cause false alarms once SAT Patrol is installed. If in doubt, give the fence a vigorous shake and listen to the noises made by the fence fabric. It is important that no “bangs and rattles” are heard. Some potential problem areas are listed below:

Slack or missing strainer wires, which will allow excessive movement of the mesh.

Missing or badly corroded fixing nuts and bolts or screws.

Loose or damaged fence posts and bracing stays.

Areas where the fence fabric is not securely fixed to its supports.

An area adjacent to the fence to which the public has access.

A highway near to the fence that carries heavy traffic during protected hours.

Large animals, i.e. cattle that may come into contact with the fence.

Signs not securely attached to the fence, Figure 3.

Trees and bushes growing against the fence, Figure 4.

Areas where rubbish can accumulate against the fence and flap in the wind.

Gaps at the bottom of the fence where an intruder could gain access without coming into contact with the fence itself.

Access gates that can rattle excessively in either the open or closed positions.

Flag poles, CCTV camera mounting posts etc that can move in the wind and transfer vibrations to the fence.

Figure 3

A loose sign on the fence, a sure cause of false alarms.

Figure 4

Bushes growing against the fence should be removed before starting to install SAT Patrol.

It is important that repairs to the fence are made before the installation commences. It will also be necessary to clear the fence of all vegetation; this can often entail a significant amount of work, and will require regular inspections after installation to ensure that bushes etc are not regrowing. If the fence is new, it is worth checking that the client has no intention of “landscaping” the site by planting trees and shrubs around the perimeter fence. In the short term this will not be a problem, but after the bushes have grown large, with many branches able to be blown against the fence, the number of nuisance alarms will rise significantly. If there is any doubt as to the suitability of a fence for the installation of a SAT Patrol system, it can often be resolved by temporarily installing a short test/demonstration zone.

The Site Installation Plan

The next step is to draw up a Site Installation Plan. This will be used to produce a Bill of Materials and provide a guide for the installation engineers. The Site Installation Plan should be commenced by showing the following information:

The line of the fence and its dimensions.

The shape and dimensions of the fence posts (if the Analyzers are to be post mounted).

Locations of gates, with type and dimensions.

The location of the building where the alarm panel will be located.

The locations of the other buildings, plant and machinery etc on the site.

Locations of any existing security systems, such as CCTV cameras, outdoor infra-red systems etc.

Routes where the interconnecting cables can be run from the Analyzers to the alarm panel.

Draw the Plan to scale, on a conveniently sized sheet (or sheets) of paper. Squared (graph) paper or a computer drawing package may be useful for this exercise. With this information drawn up and annotated, the zone planning can be carried out. When doing this, a number of factors must be taken into consideration.

  • A mandatory requirement of the SAT Patrol system is that zones should not contain more than 1000 feet (305 meters) of sensor cable. The system will work with longer zones, but its performance will be degraded, possibly seriously. Short zones are not a problem; many installations, for operational reasons, use zones of only 150 feet (50 meters).
  • When planning zones, it is necessary to provide an additional 10% sensor cable to allow for service loops at fence posts, additional cable at braced corners etc.
  • On a standard height fence, around 7 feet 6 inches (2.3 meters), a single length of sensor cable will be required. If the fence is higher than this, or the system is to be installed on a high security site, then a double trace of sensor cable must be used. This wills obviously double the amount of sensor cable required per zone. The 1000 feet maximum sensor length must still be adhered to in such cases.
  • If the perimeter is under CCTV surveillance it is advisable to match the camera zones to the SAT Patrol zones. A similar consideration applies if there is a complementary perimeter security system present, such as microwave or infra red.
  • The location of the Analyzers relative to the control panel is also important; it is advisable to locate Analyzers so as to minimize the length of interface cable required.
  • Do not mix different types of fence in the same zone. For example, a SAT Patrol zone that has chain link fencing combined with another fence fabric, such as welded mesh, will be difficult to set up and its operating efficiency will invariably be compromised. These considerations also apply if the fence changes height along its length; for example do not combine high fence with outriggers and medium height fence without outriggers in the same zone.
  • For operational reasons, the user may have his owns requirements for the number and placement of zones.
  • There is obviously an economic advantage to having longer zones, since each zone, regardless of its length, requires an Analyzer.
  • Gates should, whenever possible, be located at the ends of zones. If required, a Gate Bypass unit is available to remove gates that are being opened or closed from the detection circuit, whilst leaving the remainder of the zone protected. The Gate Bypass unit can be remotely operated by applying 12 volts DC.
  • Both single and dual zone Analyzers are available; a dual zone Analyzer will monitor two adjacent zones with up to 1000 feet (305 meters) of sensor cable in each. A dual zone Analyzer is more economical to install than two single zone Analyzers, since two electronic assemblies are mounted in one box and only one interconnecting cable has to be installed between the Analyzers and the alarm control panel.
  • Analyzers can either be mounted directly on fence posts or located some distance away from the fence. If the latter option is chosen, a length of non microphonic cable is required to connect the end of the sensor cable to the Analyzer. The length of the non microphonic cable should not exceed about half the length of the sensor cable on the fence. However, it should be remembered that setting up the system becomes a two person operation if the Analyzer is not mounted on or close to a fence post. In order to optimize the Analyzer settings it is necessary to monitor the Analyzer response when the fence is tapped sharply with a screwdriver handle; this is clearly impossible for one person to do if Analyzer and fence are not collocated.
  • In areas where there may be a high risk of the sensor cable incurring physical damage it can be protected by a conduit attached the fence. The conduit can be conventional rigid steel or the type that is flexible. Clearly the conduit must be fabricated from a material that is suitable for outdoor use. The sensor cable is available pre-installed in 9/32″ (7 mm) diameter flexible stainless steel conduit, in lengths up to 400 feet (122 meters). This is conveniently supplied on reels ready for installation using cable ties or screw fixed clips.
  • The interconnecting cable may require to be run in conduit or be steel wire armored for direct burial. The number of pairs in the cable also needs to be decided at this point; consult Section 3 on Installation and Figures 22 & 23 to decide which functions are required. If a dual Analyzer is being used, the power supply for each zone can be run on a single pair of wires.

The Installation Plan, when complete, should be a detailed drawing of how the system will be installed. It should clearly show all of the salient features of the installation, including zone divisions, zone lengths and Analyzer locations, interconnecting cable runs and lengths and any special items such as gate bypass switches. The Installation Plan should enable an installation engineer who has not had the benefit of a site visit to envision exactly how the installation is to be carried out.

Analyzer Installation

If the Analyzers are to be mounted on the fence posts, suitable mounting hardware will need to be constructed. This can consist of an aluminum plate, of between 1/8″ and 1/4″ thickness, fixed to the fence post by stainless steel worm drive bands. Figure 6. Illustrates a mounting plate suitable for most types of fence post, Figure 7 shows an Analyzer mounting plate fixed to a concrete fence post. The Analyzer should be slightly over half way up the fence. Only use the holes that already exist in the Analyzer case for mounting, drilling further holes will compromise the water resistance of the case. Alternatively, the Analyzer can be located away from the fence, mounted on a post or wall, or within a weatherproof housing. Under no circumstances attach the Analyzer directly to the fence mesh, this will give rise to false alarms. The Analyzer should always be mounted upright, with the cable glands at the bottom. Having attached the Analyzers to the fence posts, ground the case of each one to a local ground using, for example, a 3 feet long copper plated or galvanized steel rod driven into the ground beneath the Analyzer (Figure 8). Connect the Analyzer case to the grounding rod using a heavy gauge copper conductor. It is important that each Analyzer is connected to an effective ground, to eliminate false alarms from the pick up of electrical noise. When this operation has been completed, it is wise to check, using a DVM on its ohms range, that there is a low resistance electrical connection between the printed circuit board mounting plate inside the Analyzer case and the connection to the grounding rod.

Figure 6

A plate suitable for attaching an Analyzer to a fence post, using stainless steel worm drive banding.

 

 

 

 

 

 

 

 

 

 

 

Figure 7

An Analyzer mounting plate fixed to a concrete fence post.

Figure 8

Driving in a grounding rod adjacent to the Analyzer.

Sensor Cable Installation

Installing the sensor cable is best carried out as a two person operation. One person unreels the cable (Figure 9) whilst the second person attaches it to the fence. On a standard height (~7 feet) fence a single strand of sensor cable will be used; it should be fixed at a height of between 3′ 0″ and 3′ 6″ from the ground, with cable ties every 6″ to 8″ (Figure 10). For high security installations, or where the fence is higher than 7′, a double trace of sensor cable should be used, fitted at one third and two thirds fence height. In this configuration, installation of the sensor cable will start at the Analyzer and be attached to the fence, one third of the way up, until the end of the zone is reached. At the end of the zone the sensor cable goes vertically up the fence to the two thirds position, from where it is led back to the Analyzer.

Figure 9

Unreeling the sensor cable.

Figure 10

Sensor cable attached to the fence with cable ties.

The sensor cable should exit the Analyzer housing vertically, to provide a water drip leg, before being lead along the fence at the correct height. Attaching the cable to the fence with a loose tie wrap either side of each fence post is a convenient way of keeping the cable off the ground whilst it is being installed. After unreeling and loosely attaching cable to 3 or 4 sections of fence, its length can be adjusted by sliding it through the loose cable ties, after which it is attached to the fence using further cable ties positioned at the correct intervals. A cable tie wrap gun, which tensions the cable tie and trims it to length in one operation,

will greatly speed up installation (Figure 11). Set the tie wrap tool to give a low to medium tension to the tie wraps, the sensor cable only needs to be held snug against the fence. When installing on galvanized fence material, beware of tightening the sensor cable onto “spikes” of galvanizing, which may damage the cable jacket. Any spikes should be removed from the fence fabric with a file before the sensor cable is attached.

Figure 11

Using a tie wrap gun to tighten and trim cable ties.

At each fence post a “service loop” should be provided, by looping the cable vertically downwards by about a foot as it goes around the post, Figure 12. These loops of cable should be attached to the fence and care taken to avoid leaving any loose cable which could rattle in strong winds. Also avoid leaving cable in such a position that it could chafe against the posts. The cable can either be left slightly loose around the post, or it may be necessary to use a cable tie around the post itself to prevent chafing movement. The service loops should not constrain the movement of the cable relative to the fence posts. These loops serve a dual purpose. They firstly provide sufficient spare cable for a repair to be made if the sensor is cut or damaged and secondly they give an increase in sensitivity at points where the fence fabric is being held more rigidly.

Figure 12

A service loop should be provided at each fence post.

At other points where the fence is held more stiffly, i.e. where there is diagonal cross bracing, such as is usually found at corners, it is necessary to increase the amount of sensor cable used to insure that climb over protection is maintained. First of all check whether the fence material can flap against the bracing strut or post in a strong wind. If it can, use cable ties to firmly attach the fence mesh to the post to prevent the flapping, Figure 13. The sensor cable should then be looped either side of the bracing post, as illustrated in Figure 14. It is particularly important that the sensor is taken into the triangular section below the diagonal bracing post, otherwise an area of low sensitivity will be left in the fence, which may be susceptible to cut through. After taking the sensor cable around the vertical fence post, repeat this operation with the other corner brace. The cable layout should be symmetrical about the vertical post at reinforced corners.

Figure 13

Using a cable tie to attach the fence fabric to a stiffening brace.

Figure 14

Cable layout at a cross-bracing post.

When the end of the zone is reached and the cable is attached to the fence, the end of line termination resistor should be fitted. This is to enable the Analyzer to monitor the continuity of the cable throughout its length; if the cable is cut the system will give a non resettable tamper alarm. If the box mounted termination resistor is being used, simple screw terminals are used to fix the sensor cable into the box – please note that the connections are polarity conscious. (Figure 15a) Having made the connections, mount the box vertically with the cable gland at the bottom. These boxes can be mounted either on the fence adjacent to a fence post, or on a post itself. The cable should be vertical when it enters the box, to provide a water drip leg. Finally, the cable gland should be tightened and the tamper protected box cover replaced. Do not attempt to ground the metallization inside the end termination box to the fence, it will be grounded via the sensor cable at the Analyzer end. Grounding both ends of any of the cables used in the SAT Patrol system will cause problems with “ground loops” when the system is commissioned. If there is any surplus cable at the end of a zone, cut it off before joining on the end of zone termination. Do not be tempted to coil surplus cable and attach it to the fence, this will have the effect of making the fence panel excessively sensitive.

Figure 15

End of zone termination.

aGates

There are no hard and fast rules for installing SAT Patrol on gates. Wherever possible, gates should be located at the end of a zone. With a single gate at a zone end, the sensor cable should be attached to the fence close to the fence post, then run across to the swinging panel of the gate, allowing sufficient strain relief for the gate to open fully. The cable is then looped around the gate panel, where it stops in an end of zone termination, as illustrated in Figure 16. For double gates situated at a zone end, the layout shown in Figure 17 is suggested. Joint boxes or heat shrink joint kits should be used where shown to splice in a length of non-sensitive coaxial cable to go across the roadway. This cable should be protected by a conduit, or be installed in a duct to avoid damage to the jacket. Care should be taken at the points where the sensor cable goes from the stationary fence to the swinging gate section. A strain relief loop will be required and it will be necessary to avoid this loop being able to flap against the fence in high winds. Depending on the construction of the gate, it may be necessary to protect the cable at this point by passing it through a short piece of flexible conduit fixed between two small boxes attached to the fixed and swinging parts of the gate, as sketched in Figure 18. Nylon spiral wrap can also be used to provide reinforcement for the sensor cable between the fixed and moving parts of the gate. If the gate is required to be in use whilst the remainder of the system is protected by SAT Patrol, it will be necessary to use a Gate Bypass Switch to isolate the gate. The Bypass Switch should be mounted on one side of the gate and 15 to 20 feet away from it, either on a fence post or some other vertical post, and connected as shown in Figure 19. It is important that the Bypass Switch is not mounted too close to the gate itself, otherwise vibration will be transmitted mechanically from the operating gate into the protected section, leading to nuisance alarms.