An apparatus for measuring electrical variables includes an external measuring connection, and a converter that converts a plurality of measurement variables into respective electrical measurement variables of a single predefined type. A control device for controlling the converter is provided and at least one type of variable to be measured with the converter can be selected via the control device, and a converter for at least two types of variables to be measured respectively has at least one independent input stage that can be used to detect the measurement variable of the type to be measured and to convert it into a predefined or predefinable type of variable. An electrical signal provided at the measuring connection is analysed in a parallel manner with respect to at least two different criteria via at least two input stages for different types of variables to be measured.