Metalarm
™
Series 3500 Metal Detectors
23
AUXILIARY RELAY WIRING
Figure 18 shows an auxiliary 230V AC relay connected
to C of (TB1) and drawing its power from the same
power supply as the Metalarm’s power supply.
Figure 19 is variation of Figure 18 wired so that the
conveyor cannot operate when the power supply to
the Metalarm is interrupted. SW2 should be in the
down position “2” for this “failsafe” operation.
Troubleshooting
SUGGESTIONS FOR TROUBLE SHOOTING
ENVIRONMENTAL INTERFERENCE
The Metalarm Control Unit generates a high frequency
alternating field within and near the sensor coil. While
the field is strongest on the sensor coil face or in the
throat of the sensor coil, it is inherent in the sensor coil
design that a certain amount of the field exists outside
of the sensor coil. Certain environmental conditions
may sometimes affect this alternating field causing
false and erratic signals.
If after installation the unit does not work properly,
check for compliance with the following hook-up and
installation details before proceeding to the specific
causes of interference.
All cable connections should be tight on the terminal
blocks in the control unit.
The power source cables should be isolated from
varying inductive loads and should be run in a
separate conduit.
The control unit should have a good electrical
ground connection.
In certain locations more than one problem may exist
and the problems may be interrelated.
Observing the installation site and the operation of the
metal detector for repeating symptoms is very helpful
in isolating the causes of the problems.
Correlating malfunctioning occurrences is invaluable
for environmental interference trouble shooting.
Observe whether interference occurs at certain
specific times and in conjunction with a
specific activity.
Observe whether interference occurs when operated
by certain personnel or only after physical change of
the environment.
Use the following to help diagnose problems and
problem sources and to implement
corrective measures.
Basically environmental interference may be of
four types:
• Movement of Metal
• Intermittent Loops of Metal surrounding the
Sensor Coil
• Excessive Line Voltage Fluctuations
• Proximity to Severe RF Radiation Sources
MOVEMENT OF METAL
Large masses of metal such as shaker screens,
metal deflection plates, vehicles etc. may affect metal
detector operation even when at a considerable
distance from the sensor coil. Other smaller masses
of moving metal when sufficiently close to the search
unit may also cause false trips. Interference may exist
outside of the room or building and be hidden from
operators’ view, such as vehicular traffic in an alley
next to the building wall or a chain conveyor below or
above the floor, or moving metal objects in an
adjacent room.
CORRECTIVE MEASURES
• Secure moving metal objects or remove them
altogether if possible, or replace with a
non-metallic material. Re-route vehicular traffic.
• Place a metal shield securely fastened and
stationary between the sensor and the source of
interference. Place a shield as close to moving
object as possible. The size of the shield will
depend on the size of the moving object.
• Install the metal detector in another location free
from interference sources.
