METHOD OF AND APPARATUS FOR MONITORING SLAG DEPTH IN REFINING IBLE

摘要

An acoustic tube having several resonant frequencies is directed into the mouth of a refining crucible and is heated to above 100.degree.C. A microphone at the remote end of this tube receives sound passing through the tube and generates an electrical output corresponding to the sound received. This electrical output is linearized over a band width including several of the resonant frequencies of the tube and the signal is then passed through a low pass filter to eliminate parasitic oscillations and through a mixer where it is combined with a signal from a local oscillator. The intermediate-frequency signal thus produced is passed through either of a pair of band-pass filters and is displayed. The signal strength at the output is inversely proportional to the depth of slag in the crucible, as the deeper the slag the more sound is absorbed in the crucible.