Grounding the M241 System

Overview

To help minimize the effects of electromagnetic interference, cables carrying the fast I/O, analog I/O, and field bus communication signals must be shielded.

WARNING
	UNINTENDED EQUIPMENT OPERATION Use shielded cables for all fast I/O, analog I/O, and communication signals. Ground cable shields for all fast I/O, analog I/O, and communication signals at a single point¹. Route communications and I/O cables separately from power cables. Failure to follow these instructions can result in death, serious injury, or equipment damage.

¹Multipoint grounding is permissible (and in some cases inevitable) if connections are made to an equipotential ground plane dimensioned to help avoid cable shield damage in the event of power system short-circuit currents.

The use of shielded cables requires compliance with the following wiring rules:

For protective ground connections (PE), metal conduit or ducting can be used for part of the shielding length, provided there is no break in the continuity of the ground connections. For functional ground (FE), the shielding is intended to attenuate electromagnetic interference and the shielding must be continuous for the length of the cable. If the purpose is both functional and protective, as is often the case for communication cables, the cable must have continuous shielding.
Wherever possible, keep cables carrying one type of signal separate from the cables carrying other types of signals or power.

Protective Ground (PE) on the Backplane

The protective ground (PE) should be connected to the conductive backplane by a heavy-duty wire, usually a braided copper cable with the maximum allowable cable section.

Shielded Cables Connections

Cables carrying the fast I/O, analog I/O, and field bus communication signals must be shielded. The shielding must be securely connected to ground. The fast I/O and analog I/O shields may be connected either to the functional ground (FE) or to the protective ground (PE) of your M241 Logic Controller. The field bus communication cable shields must be connected to the protective ground (PE) with a connecting clamp secured to the conductive backplane of your installation.

WARNING
	ACCIDENTAL DISCONNECTION FROM PROTECTIVE GROUND (PE) Do not use the TM2XMTGB Grounding Plate to provide a protective ground (PE). Use the TM2XMTGB Grounding Plate only to provide a functional ground (FE). Failure to follow these instructions can result in death, serious injury, or equipment damage.

The shielding of the Modbus cable must be connected to the protective ground (PE).

DANGER
	HAZARD OF ELECTRIC SHOCK The grounding terminal connection (PE) must be used to provide a protective ground at all times. Make sure that an appropriate, braided ground cable is attached to the PE/PG ground terminal before connecting or disconnecting the network cable to the equipment. Failure to follow these instructions will result in death or serious injury.

Protective Ground (PE) Cable Shielding

To ground the shield of a cable through a grounding clamp:

Step	Description
1	Strip the shielding for a length of 15 mm (0.59 in.).
2	Attach the cable to the conductive backplane plate by attaching the grounding clamp to the stripped part of the shielding as close as possible to the M241 Logic Controller system base.

NOTE: The shielding must be clamped securely to the conductive backplane to ensure a good contact.

Functional Ground (FE) Cable Shielding

To connect the shield of a cable through the Grounding Bar:

Step	Description
1	Install the Grounding Bar directly on the conductive backplane below the M241 Logic Controller system as illustrated.
2	Strip the shielding for a length of 15 mm (0.59 in.).
3	Tightly clamp on the blade connector (1) using nylon fastener (2)(width 2.5...3 mm (0.1...0.12 in.)) and appropriate tool.

NOTE: Use the TM2XMTGB Grounding Bar for Functional Ground (FE) connections.