Glossary · Industrial communication
AS-Interface (AS-i)
Also known as: AS-i, Actuator sensor interface, ASi
German: AS-Interface (AS-i)
In industrial communication, AS-Interface (AS-i) is a fieldbus for connecting simple binary and analog sensors and actuators to a controller over a two-wire cable that carries both data and power. It is standardized in IEC 62026-2.
- Industrial communication
- Standards
In one sentence
AS-Interface (AS-i) is a two-wire fieldbus for simple sensors and actuators that carries data and power on one cable (IEC 62026-2).
Example
Pushbuttons, indicator lights and proximity switches on a conveyor are connected to one yellow AS-i flat cable that links them to the PLC through an AS-i gateway.
How it applies
- Engineering: AS-i sits at the lowest field level. A master (often a gateway to a higher-level Fieldbus or Industrial Ethernet) polls the slaves in a fixed cycle. Each slave needs a unique address, which is assigned during commissioning.
- Commissioning: Addressing, cable length and power supply are the typical sources of errors. An AS-i power supply with data decoupling is required; a standard power supply can't be used directly.
- Safety: A safety extension of AS-i exists for transmitting safety-related signals such as emergency stop commands. Using it doesn't make a function safe by itself; the whole Safety function still has to be designed and validated.
- Documentation: The documentation team records slave addresses, profiles and the gateway configuration in the electrical documentation and explains how to replace a slave, including how the replacement gets its address.
AS-i vs. IO-Link
AS-i is a bus: many devices share one cable. IO-Link is a point-to-point connection between one device and one master port, designed for parameterization and diagnostics of smart sensors.