| 摘要 |
PURPOSE:To obtain an eddy current-type current meter where an unbalance voltage component is reduced to improve the S/N ratio, by inserting electromagnetically symmetrical and equivalent dummy structures in a range covered by a magnetic field in the end part of a probe. CONSTITUTION:An exciting coil 3 is wound around the central part of an iron core 2, and two detecting coils 4a and 4b are wound around it on both sides of the coil 3, and positions of these coils are secured by spacers 5. A magnetic field phi of this magnet whose both ends are opened has an influence up to a space corresponding to a coil length L. If a conductor exists in the alternating magnetic field, an eddy current is generated in the conductor to cause a loss. An eddy current loss We is obtained by a formula (1). In this formula, C1 is a constant determined by a magnetic flux density and a frequency, and V is the volume of the conductor, and (b) is a length of the area where the eddy current is generated, and rhoe is a specific resistance of the conductor. Consequently, when MI cables 9 having equivalent V, (b) and rhoe are inserted in regions l1 and l2, the unbalance voltage is reduced considerably, thus realizing a high-sensitivity eddy current-type current meter where the S/N ratio of a flow signal is improved considerably. |
