Eriez Xtreme, Reference Manual

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PERMANENT CURRENT LOOPS
Permanent conduction paths (i.e. cross members) in the conveyor frame should be welded
securely to provide a reliable path for any current that may be created. Bolted construction may
eventually degrade, and is not recommended unless designed and executed by experts in
metal detector conveyor construction. Any conduction path that is to remain removable, or that
cannot be welded or permanently bolted, must be electrically isolated from the conveyor frame.
Figure 7 shows a conveyor frame properly modified for a metal detector installation. Notice
that possible breaks in the current paths no longer exist, and the only current loops in the
conveyor frame are running through a permanently welded connection. These current loops will
be constant and therefore will not cause false detections.
Figure 7
Insulated
Metal
Detector
Head
Pulley
Tail
Pulley
Electromagnetic Field
Bearings
Return Idler
Welded Frame Cross
Member
Induced/Ground
Current Path
SUPPORTING STRUCTURE
The structure that supports the metal detector sensing head must be strong, rigid, and as free
from vibration as possible. Electronically, the metal detector can be configured to ignore most
vibration. Improved sensitivity can be obtained by preventing mechanical vibration from
reaching the detector head.
MECH
19