Abstract: A method for monitoring a process plant having a fieldbus of process automation technology, via which a number of field devices exchange with a process control unit PLC telegrams in regular data traffic for process control. The following method steps are executed: telegrams transmitted via the fieldbus to the process control are tapped by a monitoring application, which performs a testing of the telegrams for data relevant for the monitoring application; data relevant for the monitoring application are processed as actual values in a process modeling application, which is part of the monitoring application; and when a significant deviation is determined between desired and actual values, an error signal is generated.

Abstract: A method for operating a field device of an industrial process, and/or automation, technology, wherein at least one communication unit is connected with the field device for sending and/or for receiving a signal. An electrical power loss of the communication unit and/or a need of the communication unit for electrical energy, especially in the form of electrical voltage, are/is reduced for an adjustable period of time. Furthermore, a communication unit, as well as to a field device with a communication unit is provided for.