Method and apparatus for measuring the length of an electrode in an electric arc furnace

A method for determining a length parameter of an electrode during operation of an electric arc furnace containing a bath, the method comprising:

• (a) providing the electrode, wherein the electrode has an upper end situated outside the furnace, a lower end situated inside the furnace, a length defined from the upper end to the lower end, and an internal duct extending along the length of the electrode, wherein the internal duct is open at the lower end of the electrode;
• (b) providing a waveguide having a first end, a second end and a solid core, wherein the waveguide is at least partly received in the internal duct of the electrode with its second end located at or proximate to the lower end of the electrode, wherein the solid core of the waveguide includes at least one target;
• (c) emitting an electromagnetic radiation signal, from a source and transmitting the emitted signal through the solid core from the first end toward the second end of the waveguide;
• (d) diffracting and/or reflecting the emitted signal from the at least one target to produce at least one return signal and transmitting the at least one return signal through the solid core from the at least one target toward the first end of the waveguide;
• (e) receiving the at least one return signal from the solid core at the first end of the waveguide;
• (f) measuring a time or frequency difference between the emitted signal and the at least one return signal;
• and
• (g) calculating the length parameter based on this difference.