OBID
®
Installation
ID ISC.ANT300/300-A
FEIG ELECTRONIC GmbH
Page 32 of 43
M01001-2de-ID-B.DOC
E N G L I S H
5.3 The influence of metal on the reading range
A magnetic field cannot penetrate metal or other magnetically conductive materials. The course of
the lines of electric flux and the inductivity of the antenna is changed and has therefore a consider-
able influence on the reading range. Furthermore, the filed is weakened by the mutual inductance
response the eddy current within the metal.
The change of inductivity may often be compensated with the help of the tuning electronics. Figure
17 illustrates the influence of a metal plate on the antenna with (upper line) and without rebalanc-
ing.
Figure 17: reading range* in dependance on the distance to metal
*Label 46 x 75 mm
2
, over the centre of the antenna, sensitivity / minimum operating field
H
min
=85mA/m rms, parallel orientation to the antenna,. transmitting power 4 W.
If metal parts cannot be avoided close to the antenna, please observe the following:
•
The minimum distance between metal and antenna is 10 cm. A distance of 30 cm will lead to a
considerable reduction in the reading range. At a distance of 50 cm to metal parts, there will be
almost no influence to be measured.
•
Metal parts must not form closed loops or electric circuits. These have to be electrically sepa-
rated at one point.
•
Metal parts in close vicinity to the antenna have to be grounded in star configuration with a
good HF-connection.
30
35
40
45
50
55
60
0
10
20
30
40
50
60
distance to metal [cm]
reading range [cm]
