List I | List II | ||
---|---|---|---|
A. | Auto collimator | I | Angular dimension |
B. | Bevel Protractor | II | Small angular displacement |
C. | Optical micrometre | III | Linear dimensions |
D. | Vernier Callipers | IV | Surface roughness |
Figure 1 shows the configuration of main scale and Vernier scale before measurement. Fig. 2 shows the configuration corresponding to the measurement of diameter $ D $ of a tube. The measured value of $ D $ is: