ABSTRACT
Intrinsic safety (IS) barriers limit the electrical energy available from wires going into a hazardous area, such that a spark from shorting the wires is not capable of igniting the hazardous atmosphere. Resistive (or “passive”) barriers, with resistors, diodes, and a fuse (sometimes the fuse is replaceable), require earth grounding and add series resistance. Resistive barriers can have resistances in the range of about 40 Ω to about 750 Ω, and can support currents of up to about 400 mA, depending on the voltage rating and the group of the hazard. Electronic (or “active”) barriers, containing active electronic circuits, do not require earth grounding, add only minimal or no series resistance, and are also available as repeaters to enable greater loop resistances. If using with a HART-enabled system, make sure that the barrier is specied as being compatible with HART™ (Highway Addressable Remote Transducer) communication, see Chapter 28.
