Shielding Of The Sensor Connecting Cable; Recommended Shielding / Grounding - ABB TTF300 Operating Instruction

TTF300 FIELD-MOUNT TEMPERATURE TRANSMITTER | OI/TTF300-EN REV. I

Shielding of the sensor connecting cable

To ensure the system benefits from optimum electromagnetic interference immunity, the individual system components, and the
connection cables in particular, need to be shielded.
The shield must be connected to the ground reference plane.
Note
National regulations and directives must be observed when grounding system components.
NOTICE
Damage to components!
In systems without potential equalization or with potential differences between the individual grounding points, multiple
instances of shield grounding can result in transient currents at mains frequency.
These can damage the shielding, influence the measurements and have a significant impact on signal transmission, of bus signals
in particular.

Recommended shielding / grounding

Grounded sensor (thermocouple, mV, RTD, Ohm), transmitter housing grounded
For ideal interference immunity, the shielding of the sensor connection cable should be connected to the sensor and transmitter
housing via a conductive connection. Sensor and transmitter housing have been grounded.
The shielding of the power supply cable is grounded at the supply isolator / DCS input directly This shielding is insulated from the
transmitter housing. The shielding of the power supply cable and the shielding of sensor connection cable must not be connected to
one another. Make sure that the shielding is not connected to ground anywhere else.
1 Temperature sensor
2 Shielding grounded via sensor
3 Sensor connection cable
4 Shielding connected to transmitter housing via a conductive connection
5 Transmitter housing, grounded
Figure 21: The shielding of the sensor connection cable has been grounded on both sides via the sensor and the transmitter housing. The shielding of the supply voltage cable is
separate from the sensor connection cable and housing.
Note
Make sure that no potential equalization can occur in the case of two-sided grounding. If this is to be expected, grounding must be
one-sided only. The system's grounding concept as well as relevant national regulations must be complied with.
WARNING
Explosion hazard
If, for functional reasons, grounding in a potentially explosive atmosphere is required by means of a connection to the potential
equalization, grounding must be on one side only.
6 Shielding insulated from transmitter housing
7 Supply voltage cable
8 Grounding point
9 Supply isolator / DCS input
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