One of the present trends in automation is the distributed, remote installation of machines and systems with the help of modular peripheral devices. This is particularly reflected by the development of the fieldbus market, where PROFIBUS is on constant course for growth. From 2004 until the end of 2007, the Profibus User Organisation has planned to double the number of installations from 10 to 20 million stations.
In 2004, more than 2.5 million new stations were installed, so that the manufacturers of Profibus devices could benefit from an annual turnover increase of 30% per cent; for 2005 the PNO is expecting further growth.
Fieldbus technology is largely concerned with remote peripheral devices, but which requirements must these meet in more concrete terms? I/O systems for the IP20 area, mounted in a protective control cabinet, are part of the well-established technology in this field. This first idea that springs to mind is to simply install these IP20 systems in a separate protective housing and to mount this directly at the machine base. This concept would surely shorten the cable routes to the peripheral sensors, but has no other distinct advantages. The user would still have to invest a lot of time to route the sensor cables, lead these through cable glands and wire them to the IP20 bus terminals. Polarity errors, which negatively affect valuable installation and set-up times, can easily occur. And if the fieldbus station is to be expanded by some other signals, then problems are bound to occur. Additional cable glands have to be integrated into the protective housing, which, at worst, may not provide enough space for such additions. And this is exactly where IP67 fieldbus devices come into play. Their percentage share within the fieldbus market is growing continuously. According to estimations, the number of fieldbus stations, which may be mounted directly in the field due to their high protecting rating, will account for 15% of the fieldbus turnover in 2005...
The author
Markus Ingenerf
is product specialist for BL67
within the product marketing
team of TURCK Headquarters
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