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Trouble Shooting
Loop Detector Application Notes SLD4
667/HQ/45200/101
16
4.
Tram Detection Applications
This section is concerned with the detection of stationary and moving trams and this section
deals with the special issues presented due to the similarity of the tram with multi-vehicles.
4.1.
Tram Detection Applications
There are two main functions that the loop can provide in tram detection applications;
8.
Stationary presence of a tram
–
used in tram stops etc
9.
Moving presence of a tram - used for holding off junctions or signs
4.2.
Basic Setup of Detector
The inductance range needs to be set for the appropriate loop channel, 1 to 4, being used for
the tram detectors. Typically the tram loops are very similar to standard traffic loops and so the
inductance most probably needs to be set to the lowest level. Links PL3 to PL6 must be set to
1-2 and 3-4, this selects the low inductance range of the detector.
4.3.
Advanced Tram Configuration Setting
If you experience difficulties with configuring the SLD4 with the tool, then refer to section 9
or the General Handbook (667/HB/45200/000) for further guidance.
4.3.1.
Gapping
When the SLD4 is set to default settings there may be some detection issues. Gapping occurs
when the detector loses the detection of the tram while the tram is still stationary or statically
over the loop.
To resolve this, lower the threshold of the detector, thus increasing the sensitivity in incre-
ments of 2% at a time until the gapping issue is resolved.
This is achieved by using the “HZ
Loop Mode” configuration.
The detector may continue to gap when the sensitivity cannot be increased, if this occurs
then the gap period needs to be covered by the output extension
3
which is found in the digi-
tal output mapping of the SLD4 configuration tool (bottom of screen). This should be config-
ured as appropriate to remove the gapping. A suitable starting point is for an 800mS output
extension.
3
The use of ‘Minimum Vehicle Gap’ has no effect on the detection output but may be useful for accurate
count statistics.