Industrial Gaussmeter IGM11 Operating Instructions
Chapter 9 Serial Interfaces
Page 51 / 106
MAGSYS
magne t
systeme
Version 01/2013
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me GmbH - All Rights Reserved.
•
The potential equalization line and the signal cable should be layed in a
distance as small as possible to each other.
•
Avoid cable extensions.
•
Conduct lines as tight as possible to grounded areas.
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:
•
16 mm² for line lengths up to 200 m
•
25 mm² for line lengths of more than 200 m
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.
•
The shields must be connected with the frame ground/earth (earthed shield
bus) for all nodes.
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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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