Каталог Weidmuller: Electronics - Analogue Signal Conditioning

Glossary
Technical appendix/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 harmonizes
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 specifications.
• Make sure that only properly categorized equipment is present within each different
zone. As soon as an area is classified as being dangerous, steps must be taken to
limit the potential ignition sources that are present there.
C
Calibration device
CE
Cold-junction compensation
Common-mode interference
Counter
A special instrument used for the calibration and configuration of analogue signal
conditioning devices. The calibration device produces highly precise standardised
signals. It is equipped with a load indicator for quick loop diagnostics.
Abbreviation for Communauté Européenne (the European Community).
Manufacturers use the CE label to confirm that their products comply with the
corresponding EC directives and the “essential requirements” therein.
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).
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.
A counter can be used for measuring flow or for counting events. Analogue or
digital input signals (pulses) may also be processed. Integrated function such as
linearisation, interference suppression, hysteresis configuration and reference values
expand the range of use of a counter. Switching contacts are available on the output
side for monitoring threshold.
W
W.25