Concept of standardised signals

Working on the premises of the basic structure of the automation system and taking into consideration the individual automation devices allocated, the question of simple and clear interconnectability of these different types of automation equipment is of some importance, particularly when considering the wide range of products on offer from the various automation equipment manufacturers. The introduction of the so-called standardised signals solves this problem. Today, these standardised signals are used worldwide by manufacturers of automation equipment.

For electrical auxiliary energy:

>> 4...20 mA (preferably)
>> 0...20 mA
>> 0...5 mA
>> 0...10 V
>> -10 V...+10 V

For pneumatic auxiliary energy:

>> 20 kPa...100 kPa or
>> 0.2 bar ...1 bar


This standard conforming representation of the integration of standardised signals into the structure of the automation system is used as a basis for the creation of the following project documentation. At the same time, it can be seen that advanced automation tools are generally moving towards the use of standardised signals, i.e. sensors immediately provide standardised signals or the actuators are directly pressurised (e.g. pneumatic actuating devices) by means of standardised signals. As such, the integration of the standardised signals shown in Picture 1 is modified so that, as shown in Picture 2, a direct connection is realised between process and process control system (elimination of measuring transducer and signal converter). The switchroom is therefore only used to provide the electrical auxiliary energy (power supply) and for the so-called routing of field signals. This routing of field signals takes place in such a way that their distribution to the basic units of the process control system used offers the best possible process reliability (redundancy thanks to favourable distribution of monitoring signals).

Picture 1: Introduction of standardised signals into automation system structure

Picture 2: Modified linking of standardised signal path in the automation system structure