Floor and Ceiling Constructions

Construction metal in the same plane as the induction loop will absorb the magnetic field. The only certain way to determine what absorption and therefore loss of signal to expect is to measure it. However, by attempting to characterise different metal construction types we can begin to make reasonable estimates.

Steel Raised Access Floors

Steel Raised Access Floor are very High Loss. They facilitate the delivery of power, telecoms data and other services precisely where required and permit easy re-configuration of the interior. They are widely used in modern office buildings and University teaching blocks.

Insert raised access floors images 1 and 2

To compensate for the very high metal losses associated with this type of flooring, multi-loops such as Univox SuperloopsSLS® , Figure 8™ and Super 8™ loops can be used. Installation is made simple with flat copper tape.

Best Practice

Although flat copper tape is insulated, it is preferable to lay the copper tape on an additional insulating layer such as gaffer tape. The copper tape can be tacked in place with glue and covered by another layer of gaffer tape or printed 'warning tape'

Steel Deck

Steel deck has a corrugated steel containment covered by a layer of concrete. There is a wide range of constructions with varying concrete depths hence signal losses from induction loop systems installed on such floor types will vary but are generally high

3 picturesfor this bit steel deck 1,steel deck 2, steel deck 3

Reinforced Concrete (Mesh)

Mesh reinforcement of concrete is probably the most common reinforcement used.The size of the mesh, the gauge of the wire and the thickness of the concrete will all have a high contribution to the magnetic field absorption , metal loss. Losses from reinforced concrete are generally in the mid range.

2 pictures Light Mesh, Heavy Mesh

Suspended Ceilings

Suspended ceilings typically rely on an aluminium grid structure to support the individual ceiling tiles. Aluminium is a very good electrical conductor, better than steel.

2 Pictures suspended ceiling 1 suspended ceiling 2

With a newly erected ceiling, the joints between the aluminium frame will be tight with little oxidation.The joints will have a low resistance, which combined with the high conductivity of aluminium means that the ceiling will absorb magnetic fields. However, over time, the constant flexing of the ceiling will loosen the joints and the aluminium will oxidise.The electrical resistance of the joints will increase. After several years, the ceiling may not present any loss to the magnetic signal from the induction loop.

BEST PRACTICE

The signal losses caused by a suspended ceiling will reduce as the ceiling ages. It is therefore, good practice to recalibrate an induction loop system mounted in proximity to a suspended ceiling every year, turning the output of the loop amplifier down each year until no loss compensation is required

GOOD IDEA

To minimise the losses caused by a suspended ceiling, run the cables in the centre of the tiles a few centimetres above the ceiling