Magnetic Autocontrol MHTM MicroDrive Access Series, Operating Instructions Manual

Page: 58 / 144

Barrier MHTM
TM
MicroDrive Access and Parking
Assembly and installation
58 5815,5013US / Version 05
8.4.2 Induction loops
The induction loops are available as ready assembled cables in
various lengths from several manufacturers. Make sure that they
meet the specification described in these operating instructions.
Alternatively a loop can be manufactured from single wire. The
following requirements must be fulfilled:

Wire cross section: 18 to 16 AWG (0.75 to 1.5 mm
2
)

Inductivity of the loop: 70 to 500 µ H. This is equivalent to a loop
with 3 to 6 windings.

When using hot pouring compounds, such as bitumen
temperature resistant loop cables/strands must be used.
8.4.3 Testing induction loops
To verify the contact resistance, insulation resistance, and
inductance of the loop these properties must be measured after
installation:

Contact resistance: 0.8 to 2.0 ohms

Insulation resistance to earth: > 1 Mohm.

Inductivity of the loop: 70 to 500 μH
If the values are not within the specified ranges, the loop is
defective.
8.4.4 Installing induction loops in bitumen, asphalt, or concrete
1. Cut a 1.97 in (50 mm) deep groove into the surface or asphalt
using a cutting disc. The groove must be equally deep at
every point. According to Fig. 14 the corners of the groove
must be cut in a 45° angle.
Fig. 18: Installing induction loop in bitumen, asphalt, or concrete
1 Groove for induction loop feed line
2 Corners cut diagonally
3 Groove for induction loop
4 Induction loop