The present invention relates to a field device (10) adapted to determine a process parameter value related to a tank, the field device (10) comprising a terminal block (26) with: a first interface (34) configured to connect to two wires (108a-b) of a loop (104); a first electrical conductor (38a) and a second electrical conductor (38b) for connecting the first interface with field device electronics (28), the second electrical conductor having a voltage drop generating element (54); a first power supply conductor (52a) connected to said second electrical conductor upstream of the voltage drop generating element and a second power supply conductor (52b) connected to said second electrical conductor downstream of the voltage drop generating element; and a second, auxiliary interface (40) adapted for wired connection to an external device (42) and configured at least for communication with said external device, wherein the second auxiliary interface comprises a communications connector (44) which is galvanicall
