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Industrial Gaussmeter IGM11 Operating Instructions
Chapter 9 Serial Interfaces
9.3.5 EIA-485 Potential Equalization Details
If you connect devices to the bus via nonisolated interfaces or if they are grounded at
various system components, or if the difference between the 0 V potentials of the
interface electronics is larger than 7 V, the data transmission might be faulty. The
devices might also be damaged.
A potential equalization between the devices is required. Please provide the following
diameters of the potential equalization of copper:
Connect the potential equalization line for all devices to ground.
9.3.6 EIA-485 Shielding Details
The shielding is for the suppression of magnetic and electric stray fields.
The stray currents are diverted to ground by the shielding.
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The potential equalization line and the signal cable should be layed in a
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distance as small as possible to each other.
Avoid cable extensions.
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Conduct lines as tight as possible to grounded areas.
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16 mm² for line lengths up to 200 m
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25 mm² for line lengths of more than 200 m
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The shields must be connected with the frame ground/earth (earthed shield
bus) for all nodes.
If in exceptional cases, there is not installed any potential equalization, the
shield must only be laid on one side.
The shield should be connected with the metal connector casing.
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MAGSYS
systeme
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