A novel temperature sensor is described, consisting essentially of a composite platinum film firmly bonded to a ceramic substrate.
The film is protected from the corrosive effects of gaseous environments by an overglaze of impervious glass, forming a device that is mechanically and thermally robust. Since the sensing unit does not require further protection by encapsulation in a metal or ceramic sheath, it responds very rapidly to thermal changes.
The sensor possesses short and long term electrical characteristics similar to those of wire-wound platinum resistance thermometers, but is less costly. It can operate over a wide range of temperatures up to about 1,000°C.
The versatile construction of the sensor renders it, in its cylindrical form, eminently suitable for monitoring the thermal changes occurring within catalyst emission control units on internal combustion engines. Dependent upon associated electronic circuitry, the device can operate visual and/or audio signals and trigger electromechanical functions informing a driver of the condition of these units.