AS-I expands to offer analogue signalling

AS-Interface, the low-level field bus system, has been enhanced to carry analogue as well as binary signals. Developers of the system say that this ability will increase AS-I`s applications without sacrificing its simplicity.

A new version of the AS-I specification includes profiles for transmitting analogue messages across seven consecutive cycles to build up a 16-bit word representing the input or output signal. Up to 126 analogue inputs or outputs can be transmitted, and binary and analogue devices can reside on the same network.

AS-I master controllers will react automatically to connected analogue slaves and each slave will be able to carry up to four analogue "channels".

The new profile can be included in coupler devices linking an AS-I network to higher level systems, enhancing the ability to collect and control analogue data.

One of the first products to support the new profile is a master controller from the German firm Bihl+Weidemann which can support up to 62 slaves and provide detailed diagnostics of peripheral faults.

The new profile does not affect AS-I`s ability to carry data and power (up to 8A) on a two wire-cable, or its connection system based on insulation-piercing "vampire" contacts.