Abstract: The invention relates to devices for detecting media. These are distinguished, in particular, by the fact that simply the medium can be detected and/or properties of the or a medium can be determined or monitored. For this purpose, a heating sensor comprising a heating device and at least one p-n junction operated in the forward direction and a reference sensor comprising at least one p-n junction operated in the forward direction are spaced apart from one another. The heating device and the p-n junctions are connected to a control device, which is a control device ascertaining the presence and/or at least one property of the medium from the thermal properties of the medium.