The basis of fault-free operation is compliant installation of the intrinsically safe incoming cables and the EMC compliant installation of the operating unit.
The interference energies coupled in on the operating unit are diverted via the functional earth connection (l/PA) on the rear.
The equipotential bonding connection rail of the HMI located at the back of the housing is internally connected with the GND supply cable (X1 pins 3 and 4).
This functional earth connection must be incorporated into the equipotential bonding by means of a short, low-resistance Cu-cable (maximum permitted cross section: 2.5mm² - 4mm²).
Otherwise, the measures taken in the device for high interference immunity and resistance to damage may become partially ineffective.
When installed in a stainless steel field enclosure, this functional earth connection must be connected to the internal equipotential bonding enclosure connection with a 2.5mm² yellow/green cable.
Figure, equipotential bonding connection:
The operating unit functional earth is fixed to the eyelet on the lower side of the enclosure.
When selecting the mounting position, ensure that the maximum possible distance is achieved from electromagnetic interference fields. This is particularly important if frequency transformers are also used.
In some circumstances, protection against "stray rays" by means of screening plates is recommended.