Question

Draw neat labeled diagrams of a Vernier caliper showing the position of external and internal jaws in the measurement of exterior and interior dimensions.

Answer 1

Vernier Caliper: A Vernier scale, named after Pierre Vernier, is a device to take measurements ‘or’ reading between two graduation markings on a linear scale by using mechanical interpolation, thereby increasing resolution and reducing measurement uncertainty by using Vernier acuity to reduce human estimation error.

Parts of Vernier caliper:

1. Lower Jaws: It is used to measure the exterior dimensions of the object, e.g., external diameter, the thickness of the sheet(s), etc. as shown in figure 1. it is designed to grip the object firmly, among the two lower jaws one is fixed and the other jaw can move. it is bigger in size.
2. Upper Jaws: It is generally used to measure the interior of the object, e.g., internal diameter, interior distances, etc. as shown in figure 2. it is smaller in size as compared to lower jaws.
3. Depth rod: It is used to measure the depth of the hole or steps. it is located at the end of the main scale.
4. Main Scale: It is supposed to be the main body of the Vernier caliper. Generally, centimeters and millimeters are graduated on this. the lowest value of the main scale is 1mm. the main scale stays stationary during measurement.
5. Vernier Scale: It is the smaller scale, mounted over the main scale which moves during measurement of any given dimensions.it is divided into N number of increments, which equals (N-1) no. of increments in the main scale. ($\therefore \left(N\right)VSD=(N-1)MSD$).
6. Thumbscrew: It is used to move the Vernier scale over the main scale. it is located at the bottom of the Vernier scale. It can move only one jaw of the Vernier caliper.
7. Lock Screw: It is mounted at the top of the vernier caliper, It is used to fix the movement of the Vernier scale over the main scale to avoid any disturbance of measurement.

• The diagram shows that the internal jaws are measuring the interior dimension.
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• The diagram shows that the external jaws are measuring the exterior dimension.
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