A GUIDE TO INFRARED BEAMS

24 May 2021

So, you are thinking of using beams but want to know which type to use?

Firstly, let’s just take 10 seconds to understand the technology. Put simply a set of beams is a torch (transmitter) and an eye (receiver), all the time the eye can see the torch it’s happy, if something gets between the two the eye switches the alarm relay.

The two main series beams can be separated into 2 groups:

TWIN BEAMS

These are the most common beams, as the name suggests they have 2 beams between the transmitter and receiver, both of which need to be broken to generate an activation. The ‘line’ of protection between the 2 units is 7cm high and 3cm wide, which needs to be completely broken to generate an activation.

QUAD BEAMS

These are the more serious beams, with 4 beams between the transmitter and the receiver. If they are installed properly all 4 transmitter points talk to all 4 receiver points so the line of protection is 33cm high and 4.5cm wide.

The first questions to ask:

  1. What distance do I need to cover?
  2. What type of terrain am I covering?
  3. How many beams should I use?
  4. What do I fit the beams to?
  5. What do I do for power?
  6. What can the beams activate?

Let’s answer these with some definitive answers and advice.

1.  Distances

TAKEX try to make life easy when it comes to using the right beam for the right distance, by using the external coverage in meters as part of the model number, so for example a PB-30TK is a beam that covers 30m outdoors, a PB-200FA will cover 200m outdoors. If you want to use the same beams indoors then that coverage distance doubles, so the PB-60TK would do 120m indoors (of course it will do 120m outdoors, but there is no guarantee that it will work proficiently as soon as you have any change in the environment).  This does mean if you have a zone 65m long, you shouldn’t lose any sleep using a 60m beam. It is always better to over-specify a beam rather than use it to the limit; for example, a 300m zone would be better protected by 2 x PB-IN-200HFA rather than 1 x PB-IN-100HFA & 1 x PB-IN-200HFA.

2.  Terrain

Beams are generally used for either site perimeters or building protection. What you have to consider is the environment the beam will be working in; is there wildlife such as badgers/foxes/domestic pets? Is the area subject to frequent mist (by water perhaps) or heavy frost in exposed locations? Is the vegetation managed? Usually these products are expected to work for many years, and I have been called out to sites where bushes and trees have grown in the zone between the transmitter and receiver. Are there any sizeable dips or rises in the length of the zone? This could leave blind spots or drop the level of protection to ground level which would then mean wildlife could be an issue. If you have a 200m zone with a big dip or rise, better to split the zone at the apex or the bottom. The idea is to try and have the beams running parallel to the ground.

3.  How Many?

There is no definitive answer to how many beams should be used per zone, which also begs the question ‘what height’? The level of risk/loss is usually reflected in the level of protection required. At a ‘Critical Infrastructure’ site I would expect to see a minimum of 3-4 beams per zone, for the majority of medium risk sites I would expect 2-3 beams, of course the minimum protection would require 1 beam per zone. Consider that if you are using multiple beams per zone, you must use beams with channel selection so there is no ‘crosstalk’. There is no ‘textbook’ answer to what height beams should be (unless it is written into the specifications), so ‘rule of thumb’ comes into play. When just one set of beams is used I usually recommend that protection covers thigh height (deliberately open to interpretation), the reason being, if it is too low there is a risk that an intruder moving with any speed may not break all of the beam path when crossing, and the chances of wildlife activating the beam is much higher.  If there are 2 beams per zone then knee height up and waist height up (again not specific).

If the specification requires protection from much lower down, it would be wise to use anti-crawl beams, these need to be broken for longer so less susceptible to problems from wildlife.

If the job is to protect windows/doors/walls then consider what is going to go through and where. Protecting the skin of a warehouse for example I would use 1 or 2 twin beams, the lower around 40-50cm from ground level, the higher one 70-100cm. Protecting windows I would expect to find a twin beam approx. 30cm from the bottom of the window. For doors it depends if the door opens into the beam path or away from it, if the doors open into the beam path the height the height is almost irrelevant, if the door opens away then a single twin beam 40-60cm from the ground, or 2 twins, the lower around 30-40 cm the higher around 80-100cm.

Protecting the top of walls to catch people climbing over either twin or quad beams, but not running along the top of the wall (where you may get large birds, cats etc.), but offset like this:

4.  Fitting

Beams can be mounted on any flat surface, on poles (ideally Ø37-43mm) or in towers (which disguise the heights and number of beams being used). The innards of the beams rotate through 180°, so you can mount beams flat to a wall and then turn the optics so the protection runs along the wall.

5.  Power

All of the standard beams require power at both ends (12-30VDC), if you have a situation where it is impossible or cost-prohibitive to get power to both ends of a zone, the alternative may be either a battery powered beam (TXF-125E) which will cover up to 100m or if it’s shorter run there are reflector beams PR-11BE (11m) or PR-30BE (30m). One thing to consider is in exposed environments subject to frost it would be worth considering adding heaters (PBH) which operate on 12-24VDC.

6.  Activation

I’m often asked what happens when someone walks through a beam, well that’s up to you. The beam is simply a switch, nothing more. What can you do with a switch?

Usually the beams are wired to a panel, and the panel determines what happens next, but you could just as easily connect the beams to a siren, a doorbell, lights, or a GSM dialler.

 

Whichever beams you use, one thing is critical; take the time to line them up properly, use a voltmeter, spending an extra 10 minutes doing a good job at this stage pays dividends.

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