Patent ID: 8400141

Claim:
An apparatus for determining and/or monitoring at least one process variable, comprising: at least one energy input, via which the apparatus receives energy for operation of the apparatus; at least one measuring unit, which measures energy applied to said at least one energy input; at least one control unit, which, based on a comparison of measured energy with a desired value of the energy requirement, controls said at least one measuring unit of the apparatus; at least one signal producing unit, which produces at least one electrical current signal; at least one test socket, via which the electrical current signal is tappable; at least one interlock diode, which is connected electrically with said at least one test socket; and at least one switch, via which said at least one test socket can be switched in or out or via which a voltage drop across said at least one test socket and/or across said at least one interlock diode is changeable, wherein: said at least one switch and said at least one interlock diode are embodied and matched to one another in such a manner, that said at least one switch shunts said at least one interlock diode in at least one switch state.