Brochure/Catalogue
Glossary
EIA-485/ RS485 EIA-485, also referred to as RS485, is an interface standard for digital, cable-
based, differential, serial data transmissions. EIA-485 uses a wire pair for
transmitting inverted and non-inverted levels for a single-bit data signal. The
original data signal is reconstructed by the receiver as the difference between
the two voltage levels. This has the advantage of increasing the resistance
to interference, since common-mode interference then has no effect on the
transmission. The EIA-485 interface operates with a voltage differential of
+/-200 mV, so that the voltage interface has a differential related to half of the
operational voltage. It normally uses a single wire pair and is operated in half-
duplex. However full-duplex operations are possible with two wire pairs.This
connection has multi-point capabilities; up to 32 nodes can be connected to
an EIA-485 bus. Standard cable lengths run up to 1.2 km in length and support
transmission speeds up to 10 MBit/s. The wire pairs must be terminated with
resistors (typically 120 Ohm) because of the cable length and high data rates.
Electrical equipment All of the electrical and electronic components and circuits within an enclosure.
Explosion groups Depending on the ignition protection, explosion-protected equipment intended
for gases, vapours and mists are divided into three explosion groups (IIA-IIB-IIC).
The explosion group provides a measure of the explosive break-though capability
of gases (in an explosive atmosphere). The requirements for the equipment
increase in strictness from II A to II C.
Explosion protection types The ignition protection type is a term used in explosion protection that refers to
the various types of protective construction designed into the product. Ignition
protection types are formulated to minimise the risk that an ignition source will
be present in an explosive atmosphere.
The following ignition protection types are specied:
• For electrical equipment in a gas
• Intrinsic safety Ex i
• Pressure-resistant Ex d encapsulation
• Increased safety Ex e
• Pressurization encapsulation Ex p
• Oil immersion Ex o
• Moulded encapsulation Ex m
• Sand encapsulation Ex q
• Ignition protection type for zone 2 Ex n
• Special ignition protection type Ex s
• For electrical equipment in dust
• Pressurization encapsulation Ex pD
• Intrinsic safety Ex iD
• Moulded encapsulation Ex mD
• Protection provided by housing Es tD
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Technical appendix/Glossary
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