UWEX 722 C Operation Manual page 12

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Short magnetic pulses, emitted by the search coil generate an electromagnetic field
around the search head which induces eddy currents into conductive objects (i.e. metal)
being within the reach of the detector.
These eddy currents cause a secondary field, showing a decay characteristic specific to
the object. The shape of the curve of the magnetic echo as a function of time depends of
size and material of the detected object and is shown in Fig. 2.
Fig. 2
At „0" a direct current is sent to the search coil generating a square wave pulse. It is cut
off at „1".The secondary field (the magnetic echo) surrounding any conductive objects
which are within detector reach will show their maximum response value at „2" after
which they decay with a characteristic shape and angle. At „3" the detector's receiver
circuit is put into operation. It detects the response signal by the search head, amplifies
the electric values and transforms them into and audible alarm signal.
In reality several hundred pulses are sent out and hundreds of single measurements will
be read every second. This allows n uninterrupted continuous search.
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© 2005, Ebinger Prüf- und Ortungstechnik GmbH.
Operations Manual UWEX
Fig. 1 : transmitted field and response field
t
ransmission pulse
0 1 2 3
Response field from mine and field decay in theory
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722 C
d
ecaying response signal from target
T