A measuring device with at least one control unit and an electrical current controller. The measuring- and operating electronics is connected to a current loop and the control unit is connected with the electrical current controller and provides the electrical current controller a reference input. The reference input corresponds to a desired value of the measurement signal current and the electrical current controller is suppliable with a primary feedback signal. The primary feedback signal corresponds to an actual value of the measurement signal current set in the current loop. The electrical current controller outputs a control signal formed from a control error signal, wherein at least one evaluation unit is provided, which compares at least one value of the control signal output by the electrical current controller with at least one reference value. The comparison indicates whether the value of the control signal exceeds or subceeds the reference value.