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入铁中,形成一个似灰体腔,使腔内铁发射率基本不变,然后利用光纤比色测温仪示出温度。