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:

Measured value using Vernier Calipers is given by $$\text{Total Reading} = \text{MSR} + (\text{VSR} \times \text{LC}) - \text{Zero Error}$$.

From Fig. 1 (Zero Error and Least Count):

$$\text{Zero Error} = 0$$

$$1\text{ MSD} = \frac{1\text{ cm}}{10} = 0.1\text{ cm}$$

$$10\text{ VSD} = 9\text{ MSD} \implies 1\text{ VSD} = 0.09\text{ cm}$$

$$\text{LC} = 1\text{ MSD} - 1\text{ VSD} = 0.1 - 0.09 = 0.01\text{ cm}$$

From Fig. 2 (Measurement):

$$\text{MSR} = 0.1\text{ cm}$$

$$\text{VSR} = 3$$

$$\text{Value} = 0.1 + (3 \times 0.01) - 0 = 0.13\text{ cm}$$