A method of measuring the surface temperature of moving bodies without touching the surface is devised.
The thermometer consists of a thin thermo-couple placed at the center of a rounded groove formed along the center line of a sheet of copper which is held on one face of a small rectangular frame. The other face of the frame, opposite the back of the groove, is covered by a plain sheet of copper which can be heated uniformly by an electric heater, its temperature being measured by another thermo-couple. The interior surfaces of these copper sheets and the groove surface are gold plated, the rest parts being coated black.
This contrivance with the groove side as the front is placed near the body of which the surface temperature t°C is to be found. Let the temperature of the plain copper sheet be θ°C and that read by the couple in the groove be τ°C. Then t _??_ τ _??_ θ, and if the temperature difference t-θbe small enough, it will become proportional to τ-θ, that is, the relation between τ and θ will be linear represented by a straight line on a graph with τ and θ as coordinates. The temperature t°C is then indicated by the intersection between this straight line and the straight line θ=τ. The temperature t°C can also be obtained on a graph with and τ-θ as coordinates.
