fieldbus solutions
5 Three generations of field device are now in use in the process industries. Firstly, there are the classic,conventional sensors and actuators with analogue 4-20mA signals and, secondly, the HART transmitters and
positioners. The Foundation Fieldbus H1 and Profibus PA, the third generation of field device, were recently
introduced. The predominant types of protection for explosion protected sensors and actuators continue
to be intrinsically safe Ex i and flameproof encapsulated Ex d. The FISCO Specification in accordance with
IEC 60079-27 has gained general acceptance for intrinsically safe fieldbus devices. The FISCO model was
developed for the fieldbus (H1 and PA), standardised in accordance with IEC 61158-2, the explosion protect-
ed version of which was initially viewed as an intrinsically safe bus. However, the number of connectable
devices is small. Far more current can be provided for more field devices if we do without intrinsic safety.
However, we do not need to do without the intrinsic safety of the field device connection. Appropriate solu-
tions must be provided for this. Besides the conventional IS isolators this does of course relate to Remote I/O
Systems for hazardous areas and field device
couplers for connection of H1 or PA field devices. Conventional
and HART field devices can be interfaced efficiently with higher-level systems using Remote I/O. For exam-
ple, this is possible with Profibus DP. R.STAHL now provides suitable
couplers and a fieldbus power supply
for fieldbus devices (H1 and PA). With this concept, the fieldbus is not operated intrinsically safe. This is the
only way of implementing an efficient and economical installation powering an adequately large number of
field devices. R.STAHL has made it its business to provide simple, efficient and economical solutions and
integrate these.
