LP21/LP22
Pag.
15
a
37
LP21/LP22 Installation instructions en
Sensors
6.4
Installing the induction loops
• The induction loops must be installed with a clearance of min. 15 cm to fixed metal objects and 1 m to
mobile metal objects. The clearance to the surface of the final road surface should not amount to more
than 5 cm.
• It is vital that the loop cable is installed separately from the supply lines
• A normal single pole cable with a cross section of 1.5 mm² must be used as a loop cable.
• If buried in the ground, the cable must be equipped with suitable insulation. If you use hot sealing
compound, make sure the cable has a suitable temperature stability.
• Induction loops should preferably be realised in squares or at right angles. If it is not possible to use
finished loops, they should be installed in a groove cut in the road surface as shown in the figure
below. The loop cable must be fixed well in the groove. Then fill the groove with sealing compound.
The corners should have a 45° angle to avoid damage to the cable insulation.
Fig.7: Installing the loops
• When installing the cable, comply with the number of turns specified in the table.
Scope of the induction loop
Number of turns
Smaller than 3 m
6
3 - 4 m
5
4 - 6 m
4
6 -12 m
3
Larger than 12 m
2
Tab.5: Number of turns on the loop cable
• The two cable ends leading from the induction loop to the detector (loop supply line) must be twisted
with min. 20 strokes/m.
• Avoid dividing the cable. Should is be necessary to divide the cable, protect the clamp points against
moisture penetration with cast resin collars.
30-50 mm
8 mm
