| 摘要 |
The measuring tablet of an optical digitising device is constructed so that the marked image positions are specified in two screen co-ordinate systems (X1, Y1; X2, Y2). Both co-ordinate systems lie in one plane, and are rotated through 180 DEG relative to each other, i.e. each image position is measured from two opposite sides of the measuring tablet. By forming the sum of the measured co-ordinate values (X1<*>, X2<*>; Y1<*>, Y2<*>) and testing the sum to be within specified limiting values, measuring errors can be identified. The invention is explained using as an example an operating device which works on the magnetostrictive principle, and in which the individual co-ordinate measured values are determined using time division multiplexing. <IMAGE>
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