Tablet Using Matteucci Effect of Amorphous Magnetic Wires

This article describes a new tablet for inputting handwritten characters to computers using amorphous magnetic wires employing the Matteucci effect, which is sensitive to perpendicular ac magnetic fields. The Matteucci voltage eM with a double-frequency-pulse shaped ac voltage is induced across the ends of an amorphous wire when an arbitrary point is vertically magnetized by a pen-shaped coil with an amorphous magnetic core. The value of eM was nearly constant as the pen was slid along the wire, but rapidly decreased with pen displacement vertical to the wire. An amorphous wire matrix was constructed, with each of the ten wires in the X and Y directions spaced at 5 mm intervals, and with Matteucci voltage pulses converted to dc voltages through peak-holders. Handwritten characters are displayed on a microcomputer display using a multiplexer, A/D converter, and position detection software.