Wallace Perimeter Security ALPHA - Page 143

Alpha/Delta (Kinetic Operator) Installation and Maintenance Manual Revision 1 - MAY 2023
143
INSTALLING VEHICLE DETECTORS AND LOOPS
9. This guide is wrien from a design perspecve, but installaon workmanship pracces are equally
important to ensure proper operaon and long loop life. The best way to ensure a quality installaon
is to employ a professional installer experienced with detector loops. A few important pracces are:
• The slot in the surface of the road should be cut ¼-inch wide x 1½-inch deep (6.3 x 38.1mm).
• The corners of the cut must be at an angle or core drilled to relieve stress on the wires.
• Aer the wire is installed, the slot must be completely backlled with a non-hardening sealer. If
the loop wires are able to move in the slot aer the sealer has set, the detector may give false
calls.
Figure 40. Loop Sealant Applicaon
Detector Logic
HySecurity recommends that vehicle detectors be used for free open and obstrucon sensing logic only.
Because of their slower speeds, closing logic is a poor choice for security gate systems. Since there are
several ways that the gate may be le standing open and because there is a loss of safety, our circuit has
not been designed to accommodate “detect to close” logic.
Loop Diagnoscs
The following tests cannot guarantee a funconing loop, but failure of either test means that the loop is
denitely suspect, even though it may sll be funconing at the me.
1. Test the resistance of the loop and lead-in wire. It should not exceed 4 ohms.
2. Test the resistance between the loop and earth ground with a 500V Megohmmeter. It should be 100
Megohms or more. Loops may funcon at less than 100 Megohms but will not be reliable (e.g., when
the ground is wet from rainfall). Low resistance indicates broken or moisture-saturated insulaon.
This is common if inappropriate wire insulaon has been used.
A schemac for a slide gate loop layout is shown in Figure 41.