Siemens CP 243-2 Instruções de Operação descarregar pdf (Página 8)

8

AS-Interface –

The perfect solution

2.

Before the task of developing a bus sys-

tem, for the lowest field level which

was both open and manufacturer inde-

pendent (just like Ethernet or

PROFIBUS) could be undertaken, a sim-

ple problem had to be solved: Compo-

nents supplied by a wide range of dif-

ferent manufacturers which all had to be

connected to the same bus system

were not necessarily able to communi-

cate smoothly with one another and

with the system.

AS International Association

In 1990, eleven renowned companies

active in the sensor and actuator field

formed a consortium to make their com-

ponents compatible.

That AS-Interface project gave birth to

the AS International Association whose

main tasks lay in, international stan-

dardisation, continued development of

the system and certification of products.

The user can recognise tested and cer-

tified products by the AS-Interface

“shadow logo” and a test number.

Requirements of AS-Interface

At the lowest control level, sensors,

contactors, motor circuit switches, indi-

cator lamps, pushbuttons etc. which

transfer volumes of information in the

bit range had to learn to communicate.

The bus systems already in existence

were either over dimensioned or simply

could not be used for such a task. They

used cables that were either too ex-

pensive or unsuitable for a direct link to

the process (e.g. fibre-optic cable,

shielded and non-flexible cable), and the

volumes of data transmitted were sim-

ply too high. Either the data protocols

were non- deterministic or the control

electronics used were much too expen-

sive if each binary sensor was to be a

bus node and in an automation network

there might be any number of them.

Over and above that, assembly and in-

stallation needed to be as simple as pos-

sible, without the need for any special

training. The costs for each connection

should be low and in keeping with the

volume of data to be transferred.

In short: AS-Interface had to be able to

network binary sensors and actuators

and link them to the higher control lev-

els, very simply, inexpensively, and

meeting industrial requirements.

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