The thermoresistive materials used for measuring temperature in the field of application up to 1400° C. are mechanically unstable and, thus, typically cannot be used as self-supporting temperature sensor elements. Therefore, they are typically mounted in protective tubes or on or between substrates. These are usually ceramic substrates. Known temperature sensors that are suitable for exhaust gas are thermoelements, which are typically made of precious metal wires of Pb/PtRh or Ni/CrNi, whose connecting legs are mutually insulated in ceramic tubes and whose contact point is protected by a metal casing or ceramic casing or by being welded into the metal casing of a sheathed type glow plug. Further known are temperature sensors designed as thick or thin layer elements, where the temperature-sensitive functional layer is vapor deposited or sintered on or between the substrates. This requires a certain (thermal) inertia of the thermoelements on the part of the respective carrier material.
Furthermore, it is quite difficult to measure temperature during the combustion processes in the combustion chamber of combustion engines. Particularly in the case of modern four-valve direct injection engines, there is often no possibility to provide an additional borehole for the access to the combustion chamber for a temperature sensor.
Moreover, the temperatures or the temperature ranges from −40 to 1400° C. to be measured, in conjunction with an aggressive atmosphere in the form of hot gas place extremely high demands on corresponding temperature sensors.