Beckhoff CX50x0 Manuel d'utilisateur télécharger pdf (Page 18)

Safety barriers – cross-zone circuits

14 CX50x0 units in potentially explosive areas

4.6.3 Temperature class

The temperature class is also relevant to the determination of usability. The temperature of a heated surface is

decisive for classification into the appropriate temperature class. The rule is that the next higher temperature

class includes all lower classes.

4.7 Safety barriers – cross-zone circuits

The connection of signal transducers (sensors) from zone 0 and 1 to evaluation units (fieldbus devices) from

zone 2 is subject to special conditions, which are coarsely outlined here. Only intrinsically safe circuits may be

used in zones 0 and 1.

A circuit is considered to be intrinsically safe if neither a spark nor a thermal effect can cause the ignition of a

certain explosive atmosphere. One of the most important measures when constructing intrinsically safe circuits

is the safe isolation of all intrinsically safe circuits from non-intrinsically safe circuits.

If an intrinsically safe circuit from zone 0 or 1 is to be connected to a non-intrinsically safe device in zone 2, the

circuit must be routed through a safety barrier. This ensures the adequate isolation of intrinsically safe and non-

intrinsically safe circuits. The following illustration shows an exemplary arrangement.

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Beckhoff CX50x0 Manuel d'utilisateur Page 18