Field device electronics for a field device used in automation engineering

A field device of automation engineering comprising:

• a field device electronics, including:
• a first terminal and a second terminal for connecting the field device electronics to a cable so that an electrical input current is suppliable to the field device electronics via the cable and a terminal voltage can be applied across the first and second terminals;
• a series regulator to set the input current so that data, including a measured value and/or parameter values, are transferable via the cable based on the electrical input current;
• a shunt regulator following the series regulator;
• a first capacitance connected in parallel with the shunt regulator for energy storage;
• a supply circuit connected in parallel with the shunt regulator and the first capacitance for providing an operating voltage;
• a control and evaluation unit connected after the supply circuit and supplied with the operating voltage, wherein the control and evaluation unit includes at least one microprocessor adapted to register a buffer voltage across the first capacitance or to register a variable dependent on the buffer voltage and, based on the registered buffer voltage or a variable dependent thereon, to make a decision concerning at least one part of the field device electronics;
• and
• a comparison circuit adapted to register a transverse current in a first transverse branch in which the shunt regulator is arranged, and further adapted to perform a comparison of the transverse current with a threshold value and to provide a signal that shows a comparison result to the control and evaluation unit, wherein the control and evaluation unit is further adapted to register the buffer voltage or the variable dependent thereon as needed based on the signal.