The invention relates to a measuring device, in particular a temperature measuring transducer, comprising an electrical resistor, which alters its value based on a chemical or physical variable that is to be measured and which is connected to an evaluation device via at least three lines. Said evaluation device checks the lines for line breaks and if such a break has occurred, switches from a four-wire circuit to a three- or two-wire circuit as required, in order to permit the continuation of the measuring operation. This improves the reliability of the measuring device.