Brochure/Catalogue

Glossary
ATEX The ATEX directive from 23.4.1994 is valid within the EU and the EFTA Western
European nations. It applies to devices, machinery components, controllers
and protective systems that are to be used in hazardous areas. This directive
harmonises the different national regulations from the EU member nations
concerning the proper and intended use of machines and facilities in hazardous
areas.
ATEX is derived from the phrase “ATmosphere EXplosive”. It stipulates that
operators should prevent explosions and ensure protection.
Regarding explosion protection in a potentially explosive atmosphere, the ATEX
directive 94/9/EC has precedence over machinery directives and must be
followed The directive describes the following steps:
• Describe how often a potentially explosive atmosphere occurs and where it
occurs.
• These areas are then divided into zones according to the specications.
• Make sure that only properly categorised equipment is present within each
different zone. As soon as an area is classied as being dangerous, steps must
be taken to limit the potential ignition sources that are present there.
C
Calibration device A special instrument used for the calibration and conguration of analogue
signal conditioning devices. The calibration device produces highly precise
standardised signals. It is equipped with a load indicator for quick loop
diagnostics.
CE Abbreviation for Communauté Européenne (the European Community).
Manufacturers use the CE label to conrm that their products comply with the
corresponding EC directives and the “essential requirements” therein.
Cold-junction compensation Thermocouples require a temperature reference point to compensate for
unwanted “cold junctions”. The usual method for achieving this is by measuring
the temperature at the reference junction with a temperature sensor that can be
read immediately. The interfering voltage can then be compensated for in the
measurement results. This process is referred to as cold-junction compensation
(CJC).
Common-mode interference Interfering currents and voltages that can occur on the connecting cables
between electrical devices and facility components. These can then spread with
similar phase and current direction to the feed line and the return line.
Counter A counter can be used for measuring ow or for counting events. Analogue or
digital input signals (pulses) may also be processed. Integrated function such as
linearisation, interference suppression, hysteresis conguration and reference
values expand the range of use of a counter. Switching contacts are available on
the output side for monitoring threshold.
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Technical appendix/Glossary
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