AS interface

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What is AS-Interface?

AS-Interface (Actuator Sensor Interface, AS-i) is an industrial networking solution (physical layer, data access method and protocol) used in PLC, DCS and PC-based automation systems. It is designed for connecting simple field I/O devices (e.g. binary ON/OFF devices such as actuators, sensors, rotary encoders, analog inputs and outputs, push buttons, and valve position sensors) in discrete manufacturing and process applications using a single 2-conductor cable.

AS-Interface is an 'open' technology supported by a multitude of automation equipment vendors. According to AS-International Association there are currently (2013) over 24 Million AS-Interface field devices installed globally, growing at about 2 million per year.[1]

AS-Interface is a networking alternative to the hard wiring of field devices. It can be used as a partner network for higher level fieldbus networks such as Profibus, DeviceNet, Interbus and Industrial Ethernet, for whom it offers a low-cost remote I/O solution. It is used in automation applications, including conveyor control, packaging machines (e.g. Schubert's), process control valves, bottling plants, electrical distribution systems, airport baggage carousels, elevators, bottling lines and food production lines (e.g. 2SFG).

AS-Interface provides a basis for Functional Safety in machinery safety/emergency stop applications. Safety devices communicating over AS-Interface follow all the normal AS-Interface data rules. The required level of data verification is provided by dynamic changes in the data. This technology is called Safety at Work and allows safety devices and standard, non-safe devices to be connected to the same network. Using appropriate safe input hardware (e.g. light curtains, e-stop buttons, and door interlock switches), AS-Interface can provide safety support up to SIL (Safety Integrity Level) 3 according to EN 62061, CAT 4 according to EN954-1 as well as Performance Level e (PL e) according to EN ISO 13849-1.

The AS-Interface specification is managed by AS-International, a member funded non-profit organization located in Gelnhausen/Germany. Several international daughter organizations exist around the world.