| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high-accuracy flow velocity by a method, wherein an eddy-current- component voltage out of an electromotive force measured by a detecting coil is removed by a phase-rectifying operation, a gap voltage portion is removed by a high-frequency magnetic field rectifying operation and an eddy-current component voltage error is removed by using a function value which is found in advance. SOLUTION: Eddy current is generated in a conductive fluid 30, by a low-frequency AC magnetic field from an exciting coil 4, and magnetic flux in a direction which offsets the low-frequency AC magnetis field is formed. When a gap 20 between the bottom part face of a flow-velocity detector head 15 and a molten metal face 18 is identical at any point, the difference in the magnetic flux between the upstream side and the downstream side of a flow 21 is detected. When the gap 20 differs, the difference in the magnetic flux is increased or changed, and an eddy-current component voltage es is increased or changed. Then, the residual component of the eddy-current component voltage es is subtracted from a speed- component voltage ev in which the eddy-current component voltage es is separated from an electromotive force (e), via a phase rectifying circuit 9a and a phase rectifying circuit 9b. The speed-component voltage ev which is found is expressed as the equation ev=evt-αes, whereαrepresents a numerical value found in advance as a function of a gap on a standstill molten metal face.
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