Distances Of Primary Loops To Metal Constructions - ABB Wireless Proximity Switches Planning And Installation Manuallines

Planning and
Installation Guidelines
Technical Description

1.4 Distances of primary loops to metal constructions

a
b
c
d
(at any place in the metal
ring construction)
Metal ring construction
(e.g. aluminum contour frame
with plexiglas pane)
Fig. 1.6: Minimum clearance of the primary loops to metal ring constructions
(e.g. aluminum contour frame with plexiglas pane)
10 Planning and Installation Guidelines
Distance of primary loops to metal surfaces or metal gratings min.. 30 mm. Consequently, the
same distance is valid for primary loops standing vertically on metal platforms, steel-reinforced
industrial floors, etc. Especially for large steel objects a distance of > 100 mm is recommended.
Large metal surfaces (e.g. larger than approx. 50 % of the primary loop area) surrounding the
primary loop arrangement (including machine fencings made of metal) should have a minimum
clearance of 200 mm (for small primary loops) up to 500 mm (for large primary loops) to the
entire primary loop area in order not to burden the power supply too much. This distance is the
overlapping in fig. 1.2.
Inside of ring constructions with continuous electric connections the electromagnetic field
induces currents which can attenuate the energy field of the primary loops. In order to avoid an
attenuation of the electromagnetic field, the electric conductivity of those ring constructions has to
be interrupted, e.g. by inserting an isolating plastic part, unless the distance to the loops or
potentional sensor positions is large enough (see b and fig. 1.9)
In order to avoid inadmissible contact voltages at those interrupted ring constructions in the
immediate neighborhood of a primary loop, the area of the ring construction must have a
minimum clearance of 30 mm to the nearest primary loop area, if the relevant area is not larger
than 9 m² (see fig. 1.5). For larger primary loops up to 18 m² this distance has to be increased
linearly up to 120 mm.
Insulator
Minimum clearance
Primary loop
Supply line for
the primary loop
Wireless Proximity Switches / Issue: 03.2005
V 6