Automatic ruler scale calibration using a rotary machine

We combined a rotary machine with a reflecting optical sensor to built a machine that automatically calibrate ruler scales. The optical sensor is mounted on a linear motion rail along the ruler scales It identifies the marked lines on a metal ruler by detecting reflecting light intensity from the lines. Our system then finds distances between lines and counts the number of lines. The measured results were compared with the a reference length obtaining from an encoder of a precise stepping motor to measure the precision of the ruler scale. From the experiment results, the machine is shown to be capable of standard rulers grade 2 calibration. Lastly, the measurement uncertainty of the machine was analyzed.