An important requirement of Fieldbus devices is the inter- operability concept mentioned earlier. Device Description
(DD)technology is used to achieve this interoperability. The DD provides extended descriptions for each object and provides pertinent information needed by the host system.
DDs are similar to the drivers that your personal computer (PC) uses to operate peripheral devices connected to it. Any Fieldbus host system can operate with a device if it has the proper DD and Common File Format (CFF) for that device.
The most recent DD and CFF files can be found on the FOUNDATION fieldbus™ web site at fieldbus.org.
1.4Intrinsic Safety
The H1 physical layer supports Intrinsic Safety (IS) applica- tions with
H1 also supports the Fieldbus Intrinsically Safe Concept (FISCO) model which allows more field devices in a network. The FISCO model considers the capacitance and inductance of the wiring to be distributed along its entire length. Therefore, the stored energy during a fault will be less and more devices are permitted on a pair of wires. Instead of the conservative entity model, which only allows about 90 mA of current, the FISCO model allows a maxi- mum of 110 mA for Class II C installations and 240 mA for Class II B installations.
FISCO certifying agencies have limited the maximum segment length to 1000 meters because the FISCO model does not rely on standardized ignition curves.
The Enhanced Jupiter Magnetostrictive transmitter is avail- able with entity IS, FISCO IS, FNICO
3 |
