| 摘要 |
<p>A digitiser table is provided under the surface of which are located a set of parallel X-conductors (1-6) and a set of parallel Y-conductors (14-19) arranged as a grid. They may be energised by electric currents to produce patterns of magnetic field close to the surface of the table, Means (92, 93; 94, 95) enables currents of constant polarity but of varying amplitude to be applied to successive pairs of conductors. A pen or cursor (22) having sensor means (33) therein responds to the local component of magnetic field perpendicular to the surface of the table. The location of the sensor (33) between a pen of current carrying conductors is given by the ratio of the amplitudes of the currents applied to the two conductors of the pair when the resultant magnetic field component perpendicular to the surface of the table passes through a null value.</p> |
