Feig Electronic VEK FG2 Series, Operating Instructions Manual

Page: 17 / 18

operating instructions VEK FG2-1
20 12/99 FEIG ELECTRONIC GmbH
Detector responds even if loop is not covered
Possible reasons Measures
Couplings caused by
insufficient frequency
separation Verification: check frequencies of all loops with diagnostic device VEK FG2. Frequency separation of
neighbouring loops has to be at least 5 kHz (VEK V..-types) resp. 10 kHz (VEK M..-types).
Note:
For multiplex detectors (VEK M...), frequency separation is not necessary for loops of one
detector.
Remedy: re-adjust loop frequencies and check with diagnostic device VEK FG2.
Couplings caused by
insufficient distance
between neighbouring
loops Verification: the minimum distance between neighbouring loops has to be half the length of the parallel loop
edges.
Note:
There is no minimum distance between the loops of one detector for multiplex detectors (VEK
M...)
Remedye: Install loops with a greater distance in between
Interferences at the loop Verification: check fluctuations in detuning mode with the helo of diagnostic device VEK FG2. They must
not
exceed 2 increments.
Remedy: - choose another frequency level.
- Use of an 8-loop makes the loop more insensitive to interferences.
Note: compared to square loops, 8-loops reduce the responsiveness of the system!
Interferences at the loop
feeder Verification: check fluctuations in detuning position with the help of diagnostic device VEK FG2 .
Fluctuation
must not exceed 2 increments.
Remedy: - the loop feeder has to be thoroughly twisted (min. 25 turns/m).
- do not install the loop feeder together with other live leads in one cable pit.
Interferences at the
detector
Verification: check fluctuations in the detuning position witht the help of diagnostic device VEK FG2. They
must
not exceed 2 increments.
The detector must not align automatically when switching loads (e.g. barrier motor).
Remedy: - connect the detector’s supply main to another phase.
Interferences caused by
compensating current in
the armouring or other
metal parts Verification: use the diagnostic device VEK FG2, position detuning , to check frequency stability.
Fluctuations must not exceed 2 increments.
Remedy: choose the greatest possible distance between loops and armouring. The greater the distance
between armouring and loops, the lesser the influence on the loop.
In some unfavourable cases, the armouring has to be spared in the loop area.
Insufficient mechanical
loop solidity Verification: tap the surface above the loop with a beam and observe diagnostic device VEK FG2 in
detuning position with regard to possible frequency jumping or permanent detuning.
Note: changes in the loop geometry may cause positive as well as negative detuning of the detector.
Positive detuning may lead to a permanent seizure of the detector. In case of negative detuning,
the
detector becomes more insensitive. Extreme frequency jumps may lead to a re-alignment of the
detector.
Remedy: -please make sure that the loop is of sufficient mechanical solidity; there must not be any
deformations in the loop geometry when crossing it with a vehicle.
- the loop must not move compared to the ground armouring.
- for installation under paving stones, please always use finished loops.
Metallic objects in loop
area Verification: use diagnostic device VEK FG2 in detuning position to check frequency fluctuations and
-jumps caused by movements of the metallic object.
Note:
If metallic objects (e.g. manhole covers, grates, loose gates etc.) are surrounded by the loop,
their
movements may cause detunings of the resonant circuit. Should there be permanent, negative
frequency changes, the system may not recognize vehicles which do only cause minor detuning.
Remedy: - re-install loop, so that the metallic object is now outside the loop field.
- replace the metallic object by a non-metallic one.
- prevent movements of the metallic object.
(if necessary, fix manhole covers and grates by welding)