| 摘要 |
PURPOSE:To perform length measurement with high resolution without limiting a drawing-out speed by photodetecting light from a projector by plural photodetectors through marks of a tape body, and digitally converting periodic analog waveforms outputted by them and while comparing them with an analog reference level. CONSTITUTION:A measuring tape 5 has many through holes 7 lengthwise at constant pitch and the projector 13 and plural photodetectors 14 are provided across the tape 5. Then, the light which is emitted by the projector 13 is transmitted through the tape 5 and the analog periodic waveforms which are outputted by the photodetectors 14 and have a phase difference are A/D- converted 16a and 16b. At the same time, the analog waveforms are compared by a comparator 17 with a specific analog reference level and the comparison result is inputted as a section signal preferentially to the digital values to classify the parts between the through holes 7 into plural groups. Then a CPU 8 measures a drawing-out equivalent quantity roughly according to the section signal while following up the drawing-out speed of the tape 5 and also measures the tape from the digital values with high resolution, so that the arithmetic result is displayed 4.
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