Apparatus for measuring the level of the molten metal in the mold of a continuous casting machine

In an apparatus for measuring the level of molten metal in a mold of a continuous casting machine which mold is oscillated with a predetermined amplitude in accordance with the result of measurement of a separation distance between the molten metal surface and a detecting head of an eddy-current type distance measuring device arranged toward the molten metal surface in the mold, wherein said eddy-current type distance measuring device is equipped with an oscillator for generating an ac signal having a predetermined frequency and a fixed amplitude, a feedback amplifier for amplifying the ac signal and said detecting head connected in a positive feedback loop of the feedback amplifier, which detecting head has eddy-current detecting coils producing a detecting signal for said positive feedback loop and an excitation coil excited by the amplified ac signal, the improvement comprising:

• mechanical means for transmitting the oscillation of said mold to said detecting head by fixing the detecting head to the mold;
• signal separating means for separating the output of said feedback amplifier into an oscillation component corresponding to the oscillation period of said mold and a distance measurement component for measuring the level of molten metal other than said oscillation component;
• and
• circuit means for controlling the amplification degree of said feedback amplifier based upon a difference, between the amplitude value of said oscillation coponent and a predetermined reference valve, that is applied to said feedback amplifier as positive feedback value in addition to said detecting signal from said detecting head in order to maintain the amplitude value of said oscillation component at a predetermined reference value.