Novel zero calibration method of steel tape

Zero calibration plays an important role in steel tape verification. Previous studies of steel tape verification demonstrated that indication error of zero position directly affected the subsequent calibration. In view of the movable hook structure on zero position, the traditional zero scale collimation system couldn't recognize the zero scale. According to the essential requirements of the measurement, a new system based on machine vision was proposed. Standard datum planes and standard scales were designed as standard component. The float equivalent method was applied in image process. Experimental result strongly proved that this system not only meet the national standard steel tape verification regulation, but also ensured the accuracy, feasibility and effectiveness.