4
INSTRUCTION MANUAL DAAB VEHICLE DETECTOR DB402
Revision 7
Installation of vehicle loops for vehicle detector
• General
The loop is made of RK 0.75-1.5 mm
2
, heat-resistant to at least 90 degrees, and is coiled 2 or 3 times depending on the
circumference of the loop. 3 coils for circumference up to 12 m, 2 for circumference over 12 m.
Best results are obtained if the loop and connector are not joined. If this is not possible, it is very important that the joint is
fully electrically reliable and watertight. The connector can be made from the same cable as the loop and must be
twisted-pair
with at least 10 turns per metre between the loop and DB402.
The connector may also be shielded twin cable.
Layout of the loop
See chapter “Suggested vehicle loop layout” page 5.
• Channel for the loop
The loop is normally laid in a channel cut into the road surface. These channels are normally 5-7 mm wide and 35-50 mm
deep. Corners must be truncated. The track must be clear of gravel, stones and water before the cable is laid in the channel. If
necessary, the bottom of the track must be levelled to prevent future wear on the cable insulation. Take care when laying the
loop to make sure that the insulation is not damaged. If necessary, fix the loop in place before backfilling the channel.
Before backfilling the channel, test the loop with the vehicle concerned.
• Loop placement
To ensure good function, note the following:
• Minimum distance from moving metal objects such as door and gates: 1.0 metre.
• Minimum distance from stationary metal objects such as reinforcement steel: 50mm.
• The connection between the loop and the connector or joins must be completely watertight. Defects or damaged
insulation result in an unstable magnetic field and unreliable operation.
• Heating cables must not be in the loop or run parallel with the loop.
• High-voltage cables close to the loop may disrupt operation.
• The channel for the loop must not contain any other cables.
• The minimum distance from other loops is 1.0 metre. Direction-sensing loops forming a figure-of-eight must not be
connected to the DB402; the loops must be separated as illustrated below.
Min 1,0m
A
B
A
B
• Testing the loop
• Check that the loop and connection have electrical continuity. A series resistance of 0.5 Ω is normal – more than 5 Ω
indicates poor contact.
• It is important also to check the earthing of the loop and connection. Resistance to earth, measured at 500 V, must be
greater than 10 MΩ (normally 500 MΩ).
• Other
The connector of a loop may be up to 150 metres long, but sensitivity decreases with increasing length.
