FIELD DEVICE FOR DETERMINING A LIMIT VALUE

The invention relates to a field device for determining a limit value of a physical or chemical process variable, comprising a sensor unit (4) for detecting the limit value and comprising an interface (5). Here, the sensor unit (4) can be connected to a superordinate unit (6) for the purpose of transmitting a current-based sensor signal (sI) via the interface (5). According to the invention, the interface (5) comprises: a signal input (51) having a first and a second signal path (52, 53), a controllable power source (54) which is arranged in the first or second signal path (52, 53), and a resistor element (55, 55') which is arranged in parallel between the power source (54) and the sensor unit (4). The power source (54) is designed in order to control the sensor signal (sI) at the signal input (51) depending on a control signal (sv) which is output by the sensor unit (4). The arrangement according to the invention of the resistor element (55) between the power source (54) and the sensor unit (4) has the effect that, even with the presence of a parasitic impedance (Rshunt) in the sensor unit (4), the signal value (sI) to the superordinate unit (6) is not corrupted.