| 摘要 |
PURPOSE:To pick out surely a minor loop, which cause a transfer miss in relation to the distortion of a rotating magnetic field, as a defective loop, by making the driving power source voltage and the modulating frequency of a clamp voltage different between X and Y-axis coils to generate a distortion in the rotating magnetic field. CONSTITUTION:In the circuit where a circular rotating magnetic field is generated by a series resonance driving circuit, the voltage value is so modulated that the rotating magnetic field of a rotating magnetic field generating coil is changed from a minimum value to a maximum value. At this time, the rotating magnetic field has a distortion if the modulating frequency is made different between X and Y coils. A distortion is generated more effectively when the modulating frequency of positive and negative voltages +E and -E of the clamp voltage are made different. When the frequency of the normal rotating magnetic field is denoted as (f), it is sufficient if the modulating frequency is a low frequency of about f/100. A part of the locus of the rotating magnetic field for modulation of the clamp voltage becomes as shown by a dotted line and a alternate long and short dush line in the figure thus, minor loops which cause a transfer miss in relation to the intensity and the distortion of the rotating magnetic field are picked out efficiently to enhance the screening effect of defective loops. |
