A sensor is proposed which is used to detect nonequilibrium states in gases, in particular in exhaust gases. The sensor consists of a carrier plate on which four resistors are provided and connected to form a Wheatstone bridge. Two of these resistors are exposed to the gas and two are protected from it. The resistors exposed to the gas consist of a material which, on the one hand, catalyses the establishment of the thermodynamic gas equilibrium and whose resistance, on the other hand, is temperature-dependent. In the event of nonequilibrium, equilibrium is established at said resistors, and the heat of reaction occurring in this process alters the temperature and, consequently, also the value of said resistors, thereby unbalancing the alignment of the bridge. This signal is fed to a suitable evaluation circuit. <IMAGE>
