Siemens SIPART PS2 Operating Instructions Manual page 281

Device category 3
Category 3 devices must be procured such that they ensure a normal degree of safety.
Devices in this category must ensure the required degree of safety in case of frequent faults
or ones that can be normally expected, e.g. defects in the device, and avoid ignition sources.
Devices in this category are suitable for use in zone 2 or 22.
Digital
Representation of a variable in the form of characters or numbers. The functional course of
an originally changeable analog variable is simulated in predefined stages. Predefined
values are assigned to these stages. Opposite to "analog".
EEPROM
EEPROM (Electrically Erasable Programmable Read-Only Memory) is a non-volatile
electronic memory chip. EEPROMs are often used when individual data bytes change over
long time periods and need to be saved in a manner protected against power failure, e.g.
configuration data or operating hours counters.
Electromagnetic compatibility
Definition as per the EMC law: EMC is the capability of a device to operate satisfactorily in
an electromagnetic environment without itself emitting electromagnetic signals which
interfere with other devices in that environment.
Ex d
"Flameproof enclosure" type of protection. When the potentially explosive mixtures enter the
enclosure of a resource and an ignition source exists in the enclosure. The transfer of the
explosion inside the enclosure to the surrounding space must be ruled out.
● d: flameproof enclosure
Ex ia / Ex ib / Ex ic
If potentially explosive mixtures enter the enclosure of a resource, it should not lead to
ignition. Demarcation of energy and increased temperatures.
Ex n
Equipment containing energy-limiting, non-sparking contacts as well as circuits whose
contacts are supplied with limited energy.
Ex t
Dust ignition protection with "t" enclosure. Dust ignition protection where the electric
equipment has an enclosure providing protection against dust ingress and a measure for
limiting the surface temperature.
SIPART PS2 with and without HART
Operating Instructions, 02/2016, A5E00074631-AB
Glossary
281