AS-Interface expansion - System description

Extension of the AS-i cable - Introduction:
The classic AS-i bus is designed for a cable length of 100 metres. Experienced users have found out that often systems with 130 meters and more function without any problems. However, AS-i has a free topology so that there is no general installation rule for these 100 plus "x" metres. In many cases long, non-terminated cables cause reflections which overlay the AS-i messages and cause faults and message repetitions.

There are several solutions for an extension by a further 100 meters:
  1. The termination plug at the end of the cable minimises reflections. In case of only few participants its connection at the end of the cable is recommended since the voltage drop there increases with the connected load. A side effect of the bus termination is the improvement of the AS-i message quality for long cables and the use of Safety at Work components.

  2. For AS-Interface repeaters allow a cable extension by a further 100 metres. The number of possible participants remains unchanged. Each repeater has a galvanic separation which divides the network into two segments. Each segment has its own voltage supply. The master segment can thus be supplied with voltage via AS-i power supply 1 and the area behind the repeater via AS-i power supply 2. This principle allows an increase in total current per AS-i power supply and improves the voltage drop.

  3. Dual masters in the centre of the machine allow an extension of the AS-i cable by a further 100 metres in opposite directions. Distances of 200 metres can thus be linked. One side effect is that twice the number of AS-i participants can be connected.