Technology

AS-Interface technology at a glance

AS-Interface (Actuator Sensor Interface) is a standard for fieldbus communication which replaces parallel wiring. AS-Interface comprises four components: the ASi master, an ASi power supply, the yellow ASi cable and the ASi nodes. The master exchanges data cyclically with the (up to 62) connected devices (nodes). By default, each device can have four inputs for reading sensors and four outputs for controlling actuators.

The transmission medium is an unshielded, non-twisted pair, two-conductor flat cable which carries power and communications to the modules, with a low current requirement. For consumers with a higher power requirement, such as motors or valve terminals, a separate flat cable is used for carrying supply voltage.

The sensors and actuators are generally connected using piercing technology. Here the insulation of the reverse polarity protected flat cable is pierced using two insulation piercing contacts – with no prior preparation necessary. This means modules can be easily moved or added in the segment at any time.

ASi permits any bus topology. The total cable length is limited, but can be increased using repeaters, bus terminators or extenders.

When errors occur, diagnostic devices or masters with built-in diagnostics functions help to locate them in the network. If a module fails, it can be easily replaced. The module can then be automatically re-addressed by the master.