A fast-response thin film thermocouple to measure rapid surface temperature changes

A thin film thermocouple has been developed to measure rapid surface temperature change. A fine wire of Constantan was inserted vertically into a hole drilled through a steel plate and held in place by ceramic cement that acted as an electrical insulator. A thin conductive film was deposited on the surface to provide an electrical connection between the steel substrate and the thermoelectric wire. The voltage difference between this junction and a second junction kept in an ice bath was calibrated as a function of the surface temperature. Tests showed that the thin film sensors could detect a temperature rise of over 200 °C in less than 10 ns produced by a laser pulse focused on the junction. The sensors were also used to measure transient surface temperature distribution under an impacting droplet of molten aluminum.