| 摘要 |
PURPOSE:To recognize if a position detector is within an effective reader and to prevent malfunction, by locating a coil so that an effective coordinate read range between flat plates or a flat plate and AC magnetic field generator and exciting the coil in a frequency different from that of the generator. CONSTITUTION:Between flat plates 2 of a coordinate reader or a flat plate 2 and an AC magnetic field generator 1, a coil 8 is located so that an effective coordinate read range can be shown. This coil 8 is excited with a power supply 11 having a frequency different from that of the generator 1 to form two different AC magnetic fields on the flat plate 2. They are detected with a position detector 3' and branched at a branching device 9. The AC magnetic field formed at the generator 1 is inputted to a signal processor 5 via a phase comparator 4' for specified signal processing. The AC magnetic field formed with the coil 8 is inputted to a phase comparator 4'' to make phase comparison with the signal from the power supply 11, and an output signal 1 is outputted when the detector 3' is within an effective read range to prevent the generation of malfunction. |
