Fault Finding

Installation checklist for vehicle detectors

1. Check security and insulation of all joints in loops and feeders. High resistance joints (even a few ohms) cause instability of detector operation.

2. Check there is no possible movement in loops and feeder cables. If loops are installed in PVC conduit, the turns must not be able to move relative to one another.
Ensure that loop feeders are tightly twisted at least 10 T/ metre right to the point of connection to the detector.

3. Try to separate mains wiring and RF sources from the loop feeders and the voltage supply to the detector. Keep them at a distance and run them in separate conduits

4. Ensure an adequate Earth is connected to the detector even when using low voltage models. This is necessary for the lightning protection / surge suppression circuitry.

5. Ensure there is no interference (crosstalk) between units when more than one is used at a site, by increasing the sensitivity on all units temporally to “MAX” and watching for random flashes of the LED, relay “chatter” or “lock-on”. Change the “Frequency” setting to eliminate the problem.

6. Do not use the detector on “MAX” sensitivity unless required to adequately maintain detection for high-bed trucks or trailers. Consider using ASB if MAX sensitivity is required.

7. Only use the “Perm Presence” setting when necessary. This is normally required only when the detector is used as a safety for a parking boom or gate and the vehicle is likely to stop in the “danger “ area for more than a few minutes.

 

Diagnosing vehicle detector faults

Fault:  No supply voltage to unit or unit power supply faulty
Remedy:  1. Check for supply voltage at detector terminals and rectify if no supply
2. Check that detector voltage matches the measured supply
3. Replace with a new unit

Fault: Direction detection (A-B) logic or delay settings have been selected
Remedy:  1. Press the detector reset for 3 seconds on a dual channel detector. If the two channel indicators flash alternatively for a few seconds, the direction logic is active. Check the user guide to disable A-B logic or delay settings if these are not required.

Fault: Detector not tuned to a loop which may be open or short-circuit
Remedy:  1. Press the detector reset for 3 seconds to attempt to clear the fault.
2.With detector unplugged, check across loop terminals for a resistance value greater than 2 and less than 12 ohms. If there is an out of limits resistance reading then check connections and any joints between the buried loop and detector. If necessary the loop may need to be replaced.
3.If the resistance is within limits but the detector still will not tune, try re-adjusting the detector frequency alternatively to “high” then to “low” and pressing the detector reset each time.
4. If step 3 does not work replace the detector with a new unit.
5. If the new unit also does not work, the loop may lie outside the detector tuning range. Check the dimension and number of turns of wire in the loop. (Refer to loop installation guide pdf document)

Fault: The loop connection in intermittent and not reliable.
Remedy: 1. Press the detector reset for 3 seconds to attempt to clear the fault.
2.If the fault clears, the loop is currently working but may fail again later with the same flashing indication.
3. If the fault does not clear, then with detector unplugged, check across loop terminals for a resistance value greater than 2 and less than 12 ohms. If there is an out of limits resistance reading then check connections and any joints between the buried loop and detector. If necessary the loop may need to be replaced.

Fault: Detector frequency is subject to interference from another closely located loop or from electrical noise
Remedy: 1. Temporalily adjust the detector sensitivity to maximum to make the fault more apparent.
2.Re-adjust the detector frequency to another setting and pressing the detector reset each time.
3. Switch off (or remove) any other closely located detector to confirm the source of the interference
4. Switch off any electrical equipment such as battery chargers or motors to confirm the source of the interference
5. Move any loose wiring associated with the detector and check if such movement causes the detector to operate.
All loop connections must be twisted together tightly if they cause malfunction when moved.
6. Restore the sensitivity setting to “med-high” or “med-low” after the fault is cleared