From the beginning its focus was on AS-Interface. Now the company is one of the leading manufacturers of security technology and electronic components for automation with this interface.

Bihl + Wiedemann was the first company to receive AS-International certification for its AS-i Master in 1995. This Master is used as a reference for the certification of all other AS-i Slaves. In 2005, the company joined a consortium for security applications with AS-Interface.

Basic AS-Interface concept

AS-Interface is an industrial bus for automation systems. It is designed to connect standard I / O components such as binary or analog devices as well as safety I / O devices according to EN ISO 13849-1 or EN 61508.

A 2-wire flat or round cable (AS-i cable, 2 × 1.5 mm2, 16 AWG) is sufficient to connect all Slaves to the Master in any topology. This is a major advantage over conventional parallel wiring, where each individual device must be connected directly to the control system. Both data and power are transmitted using the same cable. Each slave or device has its own address for data access. These devices can be up to 31 (single addressing) or up to 62 (1A-31A and 1B-31B) in enhanced addressing. Both systems can share the same As-i network.

AS-Interface structure

The entire As-i network is controlled by a master or gateway, which acts as a direct connection to the host device (PLC, PC, DCS…). The gateway acts as a master for As-i and at the same time as a slave for a higher network level (PROFIBUS, EtherNet / IP, DeviceNet, CANopen, Modbus, etc.). As-i is here as the lowest part of the pyramid, mediating the connection of actuators and sensors.

Bihl + Wiedemann products:

• Gateways (for connection to PROFIBUS, PROFINET, EtherNet / IP, DeviceNet, CANopen, Modbus, EtherCAT, CC-Link, Serco…)
• Monitoring and security modules
• Compact safety monitors and I / O modules
• Resources

Advantages of AS-Interface

• Reducing the number of I / O cards, thus reducing the cabinet size
• less cabling
• free choice of network topology
• Quick installation, less time to commission, test and maintain
• easy extensibility
• fast signal transmission (max. 5 ms)
• without the risk of poor electrical connections
• high EMC noise resistance
• quick fault location

Characteristics of AS-Interface

• 2-conductor unshielded ribbon cable
• The signal transmits both data and power within one cable, max. 8 A
• Cable length 100 m (with extension up to 1000 m)
• The number of Slaves in the network is up to 62
• Number of digital I / O up to 248 inputs and 248 outputs
• Number of analog I / O up to 124 inputs or outputs
• One cycle time 153 us / slave
• Transmission speed 167 kbit / s
• Error Protection Identify and repeat bad packets
• Supported topologies Tree, star, circle, linear connection and network
• Safety SIL 3, Category 4, PLe (EN 62061, EN 61508, EN ISO 13849-1. EN 954-1)