The present disclosure provides an apparatus and method for the measurement of the width and radial spacing of commutator segments with respect to span. The apparatus utilizes a microprocessor and computer to record and calculate data from both a rotary encoder wheel held in contact with the commutator surface as it turns, and a fiber optic sensor that recognizes commutator segment boundaries. The commutator is rotated for one revolution plus one span to improve convenience and accuracy of the measurements. Output is provided in the form of graphs and charts that show the variation in the different spans around the commutator, and information is also provided as to each bar and insulator.