DGT / DGT60 / DGTQ / DGTP
7
2.4 EARTHING SYSTEM
For the right earthing and the optimal functioning of the system, it is necessary to ground the indicator, load cells,
eventual junction box, and the weighing structure.
INDICATOR
Ground terminal 2 (GND) using a copper cable with a section not less than 16 mm
2
.
LOAD CELLS AND JUNCTION BOX
- In the case the load cells are connected to the indicator through a junction box, it is necessary to connect the
sheathing both of cells cables and of indicator cable to the earthing of the junction box (refer to the junction box
manual) and connect this to the earth through copper cables having at least a 16 mm
2
cross-section.
- If the load cells are directly connected to the indicator (without the junction box), it is necessary to ground the
sheathing of the cell cables using copper cables having at least a 16 mm2 cross-section.
Moreover in both cases it is required to:
Connect the upper side of every cells to the lower side using a copper braid having at least 16 mm2 cross-
section; the upper side must be short-circuited with the surface of the weighing structure and the lower one
must be connected to the earth using a copper braid having at least 16 mm2 cross-section.
Use Earth plate of suitable length, in order to obtain a total resistance of earthing plant lower than 1 Ω.
WEIGHING STRUCTURE
Connect the weighing structure and the possible connected structures (for example silos that release material on the
weighing structure) to the earth through copper cables having at least a 16 mm
2
cross-section.
NOTES:
In the case the weighing system regards great and/or outdoor structures, the cross-section must be greather
(for example 50 mm2), because the voltage into play is greather (for example thunderbolts).
In order to avoid possible undesired effects, if there are other shielded cable connected to the indicator (for
instance, PC cable) the shield should be earthing only on the cable termination towards the indicator.
Every shielded cable or not (for instance PC cable, cell cable, power supply cable) connected to the indicator
should be as shorter as possible, then you have to come out of the shield the minimum length of cable, go
three round around a ferrite ring and then connect to the terminal box.
If the indicator is situated inside an electric panel, the power supply cable should be a shielded cable as
shorter as possible, distant from every coil supply cable, inverter, electromotive force, etc. and in addition
dedicate an uncoupler transformer in order to feed the indicator only.
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