PURPOSE: To execute a measurement with a high accuracy even in case of a mold whose sectional area is small, by extracting an amplitude of a vibration signal generated from a detecting head from a feedback amplifier, and adjusting an amplification degree of the feedback amplifier so that its amplitude becomes to have a prescribed value.
CONSTITUTION: When a level of a molten metal surface 2 in a mold is measured by fixing a detecting head 5 to the mold 1, an output voltage of a feedback amplifier 4 becomes a composite signal of an output corresponding to the molten metal surface level and an oscillation signal by a mold vibration. An output voltage of this composite signal is applied to a linearizer 21, and compensated so as to become an output voltage characteristic proportional to the molten metal surface level. The output voltage of the linearizer 21 is applied to an oscillation signal detector 23, too, fed back to the feedback amplifier 4 through a differential amplifier 24, etc., and compensates an amplification degree of the amplifier 4 so that its output voltage becomes zero volt. In this way, the molten metal surface level can always be measured with a high accuracy by adjusting the amplification degree of the amplifier 4 by an optional molten metal surface level.
ANDOU SEIGO
KAWASE YOSHIHIRO
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