Dual Loop Detector LD0l
User Manual
5
lnstallation Guide
Optimum functioning of the detector module is largely dependent on factors associated with the inductive
sensor loop connected to it. These factors include choice of material, loop configuration and correct
installation practice. A successful inductive loop vehicle detection system can be achieved bearing the
following constraints in mind, and strictly following the installation instructions. The detector must be
installed in a convenient weatherproof location as clase as possible to the loop.
5.1
Operational Constraints
Crosstalk
When two loop configurations are in clase proximity, the magnetic fields of one can overlap and disturb the
field of the other. This phenomena, known as crosstalk, can cause false detects and detector lock-up.
Crosstalk between adjacent loops operating from different detector modules can be eliminated by:
1.
Careful choice of operating frequency. The closer together the two loops, the further apart the
frequencies of operation must be.
2.
Separation between adjacent loops. Where possible a mínimum spacing of 2 metres between loops
should be adhered to.
3.
Careful screening of feeder cables if they are routed together with other electric cables. The screen must
be earthed at the detector end only.
Reinforcing
The existence of reinforced steel below the road surface has the effect of reducing the inductance, and
therefore the sensitivity, of the loop detection system. Hence, where reinforcing exists 2 turns should be added
to the normal loop, as referred to in section 5.3. The ideal mínimum spacing between the loop and the cable
and steel reinforcing is 150mm, although this is not always practically possible. The slot depth should be kept
as shallow as possible, taking care that the feeder remains exposed after the sealing compound has been
applied.
5.2
Loop and Feeder Specification
The loop and feeder should preferably constitute a single unjoined length of insulated copper conductor, with
a mínimum rating 1SA.
Joints in the loop or feeder are not recommended. Where this is not possible, joints are to be soldered and
terminated in a waterproof junction box. This is extremely important for reliable detector performance.
5.3
Sensing Loop Geometry
Sensing loops should, unless site conditions prohibit, be rectangular in shape and should normally be installed
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