Automation engineering two-wire field device

An automation engineering two-wire field device, comprising:

• a sensor element for capturing a process variable;
• a connection terminal for connecting a two-wire line;
• a field-device electronics unit, which is supplied with an operating power by a terminal voltage applied to the connection terminal and a loop current flowing through the connection terminal from the two-wire line, wherein the field-device electronics unit is configured to operate in a measurement mode, including communicating the captured process variable by setting the loop current to a value between 4 mA and 20 mA representing the captured process variable;
• a diagnosis unit configured to operate in the measurement mode, including capturing a value for the terminal voltage for each of at least two different values of the loop current set to between 4 mA and 20 mA, and to take exclusively the values captured in the measurement mode as a basis for making a statement about a minimum value of the terminal voltage for a maximum value of the loop current greater than 21 mA.