| 摘要 |
A digital measuring instrument includes a housing containing a measuring line, a rotatable drum engaging the line whereby movement of the line causes rotation of the drum, a storage spool mounted in the housing for storing the line, a crank assembly for rotating the storage spool for winding the measuring line about the storage spool, and a rotatable disc that rotates simultaneously with the measuring drum. The instrument includes an optical sensor in communication with the rotatable disk for compiling data related to rotation of the disk, and electronic circuitry in communication with the optical sensor for calculating a length of the line drawn from the housing. The housing has a well for receiving the storage spool and a side cover with a slideable lock for covering the well.
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