Каталог Weidmuller: Electronics - Analogue Signal Conditioning

Glossary
Technical appendix/Glossary
Hazardous area
Hysteresis
According to the ATEX directive, an hazardous area is where the extent of the
explosive atmosphere mandates that extra measures must be taken to safeguard
health and protect surrounding machinery. Hazardous areas are classified according
to the frequency and duration of the occurrence of the explosive atmosphere (refer
to the sub-divided zones).
Specifies the percent difference between the switch-on and switch-off points of a
switching contact. The hysteresis must not fall below a minimal value. Otherwise it
would no longer be possible to carry out specific switching during the monitoring
of threshold.
I
IECEx
Impulse withstand voltage
Initiator PNP/NPN switched
Insulation voltage
Intrinsic safety “i”
Intrinsically safe electrical equipment
IP protection classes
An international directive regarding the creation of declarations of conformity by the
manufacturers of facilities, devices and components that are intended for use in
explosion risk zones. This directive is valid throughout the globe but is only currently
used in some Asian nations.
The high pulse voltage of a specified form and polarity that does not lead to an
insulation breakthrough or flashover, under the specific conditions defined in
EN 60664-1.
Two wires in a three-wire sensor are responsible for keeping the supply activated.
The third connecting wire is used for transferring commands (NO/NC contact).
Initiators with NPN outputs switch the load in active mode towards the minus
potential. Proximity switches with PNP outputs switch toward the plus potential.
For electronics components with electrical isolation, this is the maximum AC test
voltage that can be applied for a specified time interval (5 s / 60 s) without causing
a break-through.
Electrical equipment for hazardous areas with the ignition protection type “Intrinsic
safety Ex i” Intrinsic safety is divided into ignition protection types “ia” or “ib”
The ignition protection type “intrinsic safety” is a protective strategy that requires
a complex analysis of electronic devices. So it is not only important to protect
intrinsically safe current from the other unsafe circuits. It is also important to limit
the open-circuit voltage, short-circuit current, power, stored energy and the surface
temperature of components that will be exposed to the explosive atmosphere.
Intrinsically safe circuits are circuits where a spark or thermal effect (as may occur
under the testing conditions specified by EN 60079-11) is not capable of igniting an
explosive atmosphere (of sub-groups IIA, IIB or IIC) or a dust-air mixture. The testing
conditions cover normal operations and certain error conditions as specified in the
standard.
Equipment that is being used directly in a hazardous area, or equipment that is
capturing signals from the Ex zone or directly controlling actuators in the Ex zone.
Equipment is assigned an IP protection class to indicate which environmental
conditions it can be used in.
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W.31