| 摘要 |
PROBLEM TO BE SOLVED: To provide a highly accurate position detecting device having a reduced position detection error periodically caused by a change in offset value with the passage of time, including in output signals of a position sensor outputting a plurality of signals having different phases and periodically changing corresponding to measurement displacement. SOLUTION: Signals DS and DC, which are digitized from output signals AS and AC through AD converters 4 and 5, are made to pass through digital low pass filters 12 and 13, thereby converting into signals SDC and CDC. A velocity transducer 14 differentiates a position signal POS to convert it to a velocity signal VEL. An offset setting means 15 sets the signals SDC and CDC as offset signals SOF and COF in a offset memory units 16 and 17 according to the value of the velocity signal VEL. Subtracters 9 and 10 eliminate the values SOF and COF, which have been set in the offset memory units, from the signals DS and DC to output signals S and C. An interpolation means carries out an arc tangent operation of the two inputs, the signals S and C, so as to convert them into the position signal POS.
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