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Notes
6.5
Installation of induction loops – procedure
Installation under asphalt or concrete:
• Size and positioning of loop(s)has been decided upon. Mark positions on the ground and check
again.
• The corners of the loops are to be executed at an angle of 45°. See Illustrations.
• By means of a cutting disk or similarly suitable tool a furrow must be cut into the road with a
depth of 50mm. the width of the furrow must allow for the cable which will be inserted at a later
point in time. The loop must lie evenly deep (parallel) with regard to road.
• The furrow must be very clean! A vacuum cleaner is ideal to remove dirt and small obstructions.
• The loop is laid with one insulated wire with a profile of 0.75mm² to max. 1.0mm² in diameter.
3 – 5 windings are laid. Now resistance and inductance can be measured.
If supply has already been installed then do a check!
• Secure loop with a plastic or wooden spatula.
ATTENTION: Do not damage cable insulation!
• Both wires are intertwined with one another in the supply line to the loop (between loop
evaluation and actual starting point of loop) in order to prevent another loop from occurring
• The supply line is led to the evaluation or is wired through the ductwork into the barrier casing
• The loop cable is now covered with fine quartz sand in order to fill the gaps between cable and
wall. At least 25mm have to remain free to road surface
• The furrow containing the loop can now be closed up. Take care when using hot potting
compound, such as bitumen! Temperatures of 90°C damage the cable isolation and destroy the
loop. Laying under interlocking stone pavement. Pay additional attention!
• There has to be enough room between the individual stones of the pavement and the loop
(30mm). The stones may move in the course of time and damage the loop.
• The loop is laid as described above with 3-5 windings – not directly into the sand but through a
customary plastic duct with a small diameter. The diameter must be small in order to prevent the
cable in the loop from moving in case of vibrations (car). The windings can also be held together
by means of cable ties. The plastic duct prevents dirt from entering due to the weight of the cars.
These measures should be prepared in the workshop and not as late as on site. The loop can
also be tested in the workshop by placing it partly under a parked car.
• The duct in which the loop is laid is to be marked and excavated. Position loop inside and cover
with fine quartz sand. Do not use grit or gravel, as these materials do not remain firm and stones
may damage the loop.
