Fieldbuses are developed for different applications, which are reflected in the process levels. The three- layer pyramid model for automation recognizes the field level as the lowest level. Above this are the process level and control level, which have different requirements for the transmission of information.
The field level is the lowest level of this level hierarchy. At this level, the control of the processes is carried out directly by the sensors and actuators. The data from the sensors are read out and processed directly for the control of the actuators or for transmission to other control units via the control units that are connected to the fieldbus. In addition to the pure sensor data, analysis and alarm data are also transmitted at the field level. Data is usually not exchanged directly between the field devices, but across levels with the control units of the actuators.