Connecting
5.3 Wiring setups for hazardous area installations
SITRANS LR250 (PROFIBUS PA)
Operating Instructions, 01/2014, A5E32221386-AB
31
Entity concept:
The Entity Concept allows interconnection of intrinsically safe apparatus to associated apparatus
not specifically examined in such combination. The criteria for interconnection is that the voltage
and current which intrinsically safe apparatus can receive and remain intrinsically safe,
considering faults, must be equal to or greater than the output voltage (Uo) and output current
(Io) levels which can be delivered by the associated apparatus, considering faults and applicable
factors. In addition, the maximum unprotected capacitance (Ci) and Inductance (Li) of the
intrinsically safe apparatus, including interconnecting wiring, must be equal to or less than the
capacitance and inductance which can be safely connected to associated apparatus.
Under the entity evaluation concept, SITRANS LR250 has the following characteristics:
(input voltage) U
i
= 24 V
(input current) I
i
= 250 mA
(input power) P
i
= 1.2 W
(internal capacitance) Ci
= 0
(internal inductance) Li
= 0
