Figure 2-1, Figure 2-2, Typical screen connections – Innotech Device Network Cabling User Manual

Page 18: Earth connection, 1 continuous screen, Typical screen connections earth connection, Figure 2-1: figure 2-2

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© Mass Electronics Pty Ltd 2007

Innotech Device Network Cabling Installation Instructions

Edition 3.0 dated 05.12.2013

Page 18

There are a number of rules that apply to the comms connection of a primary network.

Some of these are explained in detail in

Chapter 1

of this manual.

Primary network rules:

• The screen must be continuous

• Only one point earthed on the screen

• Even if a network has a number of devices with a soft earth, one hard earth is still required on that

network

• The Net and Global networks should have the same length cable run and path

• If a repeater is installed, each side of that repeater is a separate network and each requires a

bonded earth connection on the screen

• Using isolated devices, devices with isolated comms cards or using an isolated MPI does not alter

any of these rules

• There are no End of Line termination (EOL) requirements on the primary network

2-1 Continuous Screen

The screen on a primary network needs to be continuous. That means it remains unbroken along its

entire length. As there is one ‘S’ terminal on a typical primary network device both the global and net

screens are to be connected to this tie terminal.

G+

S N+

G-

N-

Figure 2-1:  Typical Screen Connections

GLB Comms

NET Comms

When there is more than one connection point to earth the screen becomes a conductor and no longer performs

correctly. Care should be taken to ensure only one bonded earth point is ever connected on a primary network.

Refer to Chapter

2-6

for details on use of a Repeater in a primary network.

NOTE

G+

S N+

G-

N-

G+

S N+

G-

N-

G+

S N+

G-

N-

Device

Device

Device

Figure 2-2:  Earth Connection

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