Abstract: A field device having a safe interface is based on two voltage regulators designed to set electrical current between corresponding contacts of the interface. The field device tests via which of the contacts the field device is connected with a superordinate unit and an automatic configuration of the interface can be performed for the appropriate transmission standard. Because the contacting to the superordinated unit is checked repetitively by means of two electrical current regulators it is assured that the field device can determine and automatically react to a change of the contacting at the interface even during measurement operation. This makes the interface safe and thereby increases the safety of the process plant, in which the field device is applied.

Abstract: The present invention relates to an apparatus for determining and/or monitoring at least one process variable of a medium, comprising a sensor unit for registering a value for the process variable, a time registration unit for registering at least one duration of operation and a calculating unit, which is embodied at least based on the duration of operation registered by the time registration unit and based on at least one influencing variable influencing the duration of operation to make at least one statement with reference to condition of at least one component of the apparatus. Furthermore, the present invention relates to a method for operating an apparatus of the invention.