A resistance temperature detector (RTD) that uses a ceramic matrix composite (CMC), such as a silicon carbide fiber-reinforced silicon carbide matrix, as an active temperature sensing element, which can operate at temperatures greater than 1000° C. or even 1600° C. Conductive indium tin oxide or a single elemental metal such as platinum is deposited on a dielectric or insulating layer such as mullite or an environmental barrier coating (EBC) on the substrate. Openings in the layer allow etching of the CMC surface in order to make high quality ohmic contacts with the conductive material, either directly or through a silicide diffusion barrier such as ITO. The RTD can measure both temperature and strain of the CMC. The use of an EBC, which typically is deposited on the CMC by the manufacturer, as the insulating or dielectric layer can be extended to other devices such as strain gages and thermocouples that use the CMC as a sensing element. The EBC can be masked and etched to form the openings. A conductive EBC can be used as the silicide diffusion barrier.