KROHNE OPTISONIC 7300 Ex EN - Manual (Page 21)

CONNECTION OF SEPARATE SYSTEMS
3
21
OPTISONIC 7300 / 8300
www.krohne.com 05/2012 - 7312262200 - AD EX OPTISONIC 7300/8300 R02
3.3 Equipotential bonding
The GFC 300 F/...-Ex ultrasonic signal converter must always must always must always must always be incorporated within the
equipotential bonding system of the installation in the hazardous classified location. For this
purpose it must be connected to the external U-clamp screw terminal (size M5) on the wall-
mounting device.
The separate bonding conductor must be at least 4 mm
2
(11 AWG) or 2.5 mm
2
(14 AWG) in case it
is mechanically protected, see Clause 413 of HD 384.4.41 or IEC 364-4-41. Make sure that the
core of the bonding wire is properly mounted under the U-clamp of the external M5 terminal and
that the screw is tightly fixed.
The transducer circuits are galvanically isolated from earth and therefore an equipotential
bonding conductor between the ultrasonic flow sensor and the ultrasonic flow converter does
not have to be connected, but can be used if desirable.
Where screened signal cable is used, the screen should only be earthed at the flow sensor end.
In the special case of a screen being earthed at both ends of the system, a potential difference
between the sensor and converter is not permitted. Refer to EN 60079-14, Clause 12.2.2.3, for
further requirements of cable screens.
Figure 3-5: Connect the cables on the signal converter.