Second, operators don't turn down the steel into the charge pad to take a sample. You pick up operating time. Bethlehem Steel's melt shops use a thermocouple to measure temperature at the first turndown. If the bath is too hot, operators add coolants such as pellet or lump iron ore, limestone, or small scrap. They'll perform another blow if the bath is too cool.
Operators use oxygen thermocouples in most heats.
This includes aluminum grades, for which the carbon levels are very high and the oxygen is very low anyway. At Bethlehem Steel, operators drop thermocouple bombs from above the vessel. The thermocouple is composed of two metals that emit different voltages as they become hot. Operators infer the temperature from the voltages. Bethlehem measures oxygen levels by inserting a probe into the bath at turndown.