Explosion-protected mini-terminator for Foundation Fieldbus H1 and Profibus PA
21 May 2008
R. STAHL's new, extremely compact type 9418 terminating resistor is suitable for explosion-protected FF H1 and Profibus PA installations. Two models for use in Zone 1 and Zone 21 are available: an Ex i terminator for intrinsically safe/FISCO fieldbus installations, and an Ex m model for power trunks that are not intrinsically safe combined with e.g. fieldbus barriers. Designed to fit in M20 cable glands, 9418 terminators can be very easily attached to cable entries, for instance in field distribution panels or field devices. Thus, users no longer need to seal unused cable entries with an otherwise required plug.
Fieldbus standards according to IEC 61158-2 call for the presence of a defined terminating resistor on both ends of a bus trunk as a measure to avoid signal reflections. While the power supply unit on one end of the bus will usually come with an integrated terminator, as is the case e.g. with R. STAHL's 9412 fieldbus power supply, the other bus end in the field must also be electrically terminated. Some devices typically found there, e.g. 9411 Ex i and Ex e field device couplers, feature built-in terminators for activation on demand. Others, such as R. STAHL's new type 9413 digital I/O coupler, require a separate one like the new 9418 terminator if they are last in line on a fieldbus trunk.
