By inserting a tube into the melted iron to form a greybody tube and to make the emissivity steady.The temperature of the melted iron can be obtained using a optical fiber thermometer.

其中一种途径即利用一个空芯导管插入铁水中,形成一个近似灰体腔,使腔内铁水表面发射率基本不变,然后利用光纤比色测温仪示出温度。