Experiment # 02
Introduction to Vernier Caliper
Introduction
A vernier caliper is a precision instrument used to measure dimensions accurately. It is widely used
in various fields such as mechanical engineering, metalworking, and science laboratories. The vernier
caliper can measure internal and external dimensions as well as depths, making it a versatile tool for precise
measurements.
Parts of a Vernier Caliper
Main Scale
The main scale is engraved on the solid L-shaped frame of the caliper. It provides the primary
measurement in millimeters or inches. The main scale is typically graduated in increments of 1 mm or 0.1
inches, depending on the system of measurement used.
Fig 1.1 Main and vernier scale
Vernier Scale
The vernier scale is a secondary scale that slides over the main scale. It provides additional precision by
allowing readings to be taken to a fraction of the smallest division on the main scale. The vernier scale is
typically divided into 10 or 20 equal parts, depending on the least count of the caliper.
Jaws
The caliper has two sets of jaws. The larger jaws are used for external measurements, such as measuring the
diameter of a cylinder. The smaller jaws are used for internal measurements, such as measuring the diameter
of a hole. The jaws are precision-ground to ensure accurate measurements.
Fig 2.2 Jaws
Depth Rod
The depth rod is a thin rod that extends from the end of the caliper. It is used for measuring depths of holes
or recesses. The depth rod is graduated in the same units as the main scale, allowing for direct readings of
depth measurements.
Fig 2.3 Depth bar
Lock Screw
The lock screw is used to hold the sliding vernier scale in position. This ensures that the measurement does
not change while reading. The lock screw is particularly useful when taking measurements that require the
caliper to be moved or adjusted.
Fig 2.4 Lock screw and retainer
Retainer
The retainer is a small device that can be used to fix the position of the jaws. This allows for consistent
measurements, especially when measuring multiple objects of the same size. The retainer helps maintain the
accuracy and repeatability of measurements.
Least Count
The least count of a vernier caliper is the smallest measurement that can be accurately read. It is typically
0.02 mm for metric calipers and 0.001 inches for imperial calipers. The least count is determined by the
difference between one main scale division and one vernier scale division.
Formula: Least Count = (Value of one main scale division) - (Value of one vernier scale division)
Fig 2.5 least count
How to Use a Vernier Caliper
1. Close the jaws and check for zero error. If the zero on the vernier scale does not align with the zero
on the main scale, note the zero error.
2. Place the object between the jaws for external measurement. Ensure the object is perpendicular to the
jaws for an accurate reading.
3. Read the main scale and vernier scale to get the measurement. The main scale provides the whole
number, while the vernier scale provides the fractional part.
4. For internal measurements, use the smaller jaws. Insert them into the object and gently open the jaws
until they touch the internal surfaces.
5. For depth measurements, use the depth rod. Extend the rod into the hole or recess and read the
measurement from the scales.
6. Apply any zero error correction to the final measurement to ensure accuracy.
Example 02 Measurement:
Suppose you need to measure the diameter of a cylindrical object. First, close the jaws
and check for zero error. Then, place the object between the larger jaws and ensure it is
perpendicular to the jaws. Read the main scale, which shows 11 mm, and the vernier scale,
which aligns with the 0.65 mm mark. The total measurement is 12.06 mm. If there is a zero
error, apply the correction to get the final measurement.
Fig 2.6 Example 1
Calculation:
Example 02 Measurement:
Suppose you need to measure the diameter of a cylindrical object. First, close the jaws
and check for zero error. Then, place the object between the larger jaws and ensure it is
perpendicular to the jaws. Read the main scale, which shows 3 mm, and the vernier scale, which
aligns with the 0.6 mm mark. The total measurement is 3.6 mm. If there is a zero error, apply the
correction to get the final measurement.
Fig 2.7 Example 2
Calculation:
Example 03 Measurement:
Suppose you need to measure the diameter of a cylindrical object. First, close the jaws
and check for zero error. Then, place the object between the larger jaws and ensure it is
perpendicular to the jaws. Read the main scale, which shows 25 mm, and the vernier scale,
which aligns with the 0.9 mm mark. The total measurement is 25.9 mm. If there is a zero error,
apply the correction to get the final measurement.
Fig 2.8 Example 3
Calculation:
