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Safety BarriersSeries 9001, 9002, 9004 Engineering

Selection Criteria Selection of industrial safety barriers is generally carried out in two steps:•Functional consideration•Safety consideration 1. Functional consideration Safety industrial barriers are first selected according to their electrical requirements. It is therefore necessary to know the electrical data of the connected apparatus. Further selection criteria:•Polarity of the voltage at the safety barrier U
N (+, -, ~) in reference to ¿ /PA•Voltage U
N •Max. permissible voltage drop across the barrier, caused by the line resistance R
L and / or a constant voltage drop ã U•Type of signal to be transmitted;voltage signals can only be transmitted via barriers with purely resistive line resistance; this limitation does not apply to current signals.
09934E02 It is furthermore to be examined, if the circuit may be grounded or if an earth-free („floating“) circuit is required due to electrical or measurement reasons. An earth-free („floating“) circuit can usually be established by using a dual-channel safety barrier or interconnecting two single-channel safety barriers.
09935E02 09936E02 Grounded circuit Floating circuit For many standard application in industrial instrumentation special safety barriers are available, which are designed optimally for the respective application according to the criteria mentioned above. 2. Safety consideration The safe maximum values of an individual safety barrier (single- or dual-channel) are determined by the certification:•Maximum voltage U
o •Maximum current I
o •Maximum power P
o •Maximum permissible capacity C
o •Maximum permissible inductance L
o It is to be tested however, if the permissible safe maximum values of the intrinsically safe apparatus (field apparatus in the hazardous area) are maintained by the selected safety barrier.
09938E02

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General Catalogue 07.12.2005