Vernier Calliper

Vernier Calliper is a precision measuring instrument used to measure the internal and external dimensions of an object. It consists of two main parts: 

• A Fixed Jaw
• A Movable Jaw

The fixed jaw is used to measure the outside of an object, while the movable jaw is used to measure the inside of an object. This is a device that is used to measure very smaller values and it can measure the value in the range of 0.1 mm. 

In this article, we will learn about Vernier Calliper, its diagram, working, and others in detail.

What Is Vernier Calliper?

A device that is used to measure very small distances is called the vernier Calliper this is a device that is used to measure distances accurate to 0.1 mm. This device was invented by the famous French mathematician Pierre Vernier in 1631 and hence its name is Vernier Scale. The vernier Calliper is shown in the image added below,

Vernier Calliper Diagram

The image added below shows a vernier calliper.

Parts of a Vernier Calliper

The main parts of a vernier Calliper are:

• Main Scale: The main scale is a graduated scale that is used to measure the overall length of an object.
• Vernier Scale: The vernier scale is a second scale that is used to measure small increments of length.
• Fixed Jaw: The fixed jaw is the stationary jaw of the vernier Calliper. It is used to measure the outside of an object.
• Movable Jaw: The movable jaw is the movable jaw of the vernier Calliper. It is used to measure the inside of an object.
• Zero adjustment screw: The zero adjustment screw is used to ensure that the Vernier Calliper is properly zeroed before taking a measurement.
• Locking Screw: The locking screw is used to secure the movable jaw in place after taking a measurement.
• Lower Jaws: The jaws of the vernier caliper, a key feature, include a fixed jaw connected to the main scale and a movable jaw connected to the vernier scale. Designed for a secure grip, the lower jaw primarily measures outer dimensions like diameter, width, and length.
• Upper Jaws: Smaller than the lower jaws, the upper jaws, attached to the top of the vernier scale, include a fixed and a movable part. Primarily used for measuring inner dimensions, the upper jaws are opened to touch the edges of objects like hollow pipes and jars for accurate readings.
• Depth Screw: Measure jar depths easily with the depth rod at the end of the main scale. Place the scale’s edge on the object’s top surface, open the jaws until the depth rod extends to the bottom for an accurate reading.
• Thumb Screw: The thumbscrew, at the bottom of the vernier scale, ensures a secure grip for easy sliding of the jaws.
• Lock Screw: The lock screw’s primary role is to secure the jaws in place once the object is firmly held, facilitating accurate readings.

How to Use a Vernier Calliper

To use a vernier Calliper, follow these steps:

Step 1: Make sure that the vernier Calliper is properly zeroed. To do this, loosen the locking screw and adjust the movable jaw until the zero mark on the vernier scale aligns with the zero mark on the main scale.

Step 2: Place the object to be measured between the fixed and movable jaws.

Step 3: Tighten the locking screw to secure the movable jaw in place.

Step 4: Read the measurement from the main scale and the vernier scale. The main scale will give you the overall length of the object, while the vernier scale will give you the small increments of length.

Least Count of a Vernier Calliper

The least count of vernier Calliper is the smallest measurement that can be made with the instrument. It is calculated by dividing the smallest division on the main scale by the number of divisions on the vernier scale.

The mathematical formula for the Least Count of Vernier Calliper is,

VC = 1 MSD – 1 VSD

If there are n divisions on the Vernier Scale then if they coincide with (n-1) division on the main scale, now the  least count of the Vernier Scale  is,

LC = (1 – {n-1}/n)MSD

Where,

• VC is Vernier Constant
• MSD is Main Scale Division
• VSD is Vernier Scale Division
• LC is Least Count

For example, if the main scale has divisions of 1 mm and the vernier scale has 25 divisions, then the least count of the vernier Calliper is 0.01 mm.

What is Zero Error?

We define zero error as the condition in which the measuring device registers a reading when there should not be any reading. There are two types of zero errors that are,

• Positive Zero Error
• Negative Error

Positive Zero Error

In the case of the positive zero error, the reading is positive and away from the actual reading of 0.00 mm. That is if the reading is 0.06 mm in this case, then the zero error is +0.06 mm.

Negative Zero Error

In the case of the negative zero error, the reading is negative and away from the actual reading of 0.00 mm. That is if the reading is 0.06 mm in this case, then the zero error is -0.06 mm.

Zero Error in Vernier Callipers

Zero error in vernier Callipers is the error that occurs when the jaws of the Calliper are closed and the zero mark on the vernier scale does not coincide with the zero mark on the main scale. Zero error can be either positive or negative. Positive zero error means that the vernier scale is ahead of the main scale, while negative zero error means that the vernier scale is behind the main scale.

In the case of the Vernier Calliper, the zero error is calculated using the formula,

Actual Reading = Main Scale + Vernier Scale

Applications of Vernier Callipers

Vernier Callipers are used in a variety of applications, including:

• Manufacturing: Vernier Callipers are used to measure the dimensions of parts in manufacturing.
• Engineering: Vernier Callipers are used to measure the dimensions of structures and components in engineering.
• Science: Vernier Callipers are used to measure the dimensions of objects in science experiments.
• Construction: Vernier Callipers are used to measure the dimensions of materials in construction.

Safety Precautions

When using a vernier Calliper, it is important to take the following safety precautions:

• Always use a vernier Calliper that is in good condition.
• Do not use a vernier Calliper to measure objects that are too large or too small for the instrument.
• Do not use a vernier Calliper to measure objects that are sharp or pointed.
• Do not use a vernier Calliper to measure objects that are hot or cold.
• Store a vernier Calliper in a safe place when not in use.

How to Read Vernier Calliper?

To ensure accurate measurements, begin by verifying the alignment of the main and vernier scales with nothing in between. When both scales read zero, zero error is eliminated. Introduce a ball between the vernier scale jaws, aligning the 0 mark on the vernier scale with the main scale to obtain the main scale reading. Identify the point on the vernier scale aligned with the main scale for the vernier scale reading. Note that readings often involve decimals, with the number before the decimal indicating the main scale reading and the number after the decimal representing the vernier scale reading.

Solved Examples on Vernier Callipers

Example 1: A Vernier Calliper with no zero error is used to measure the diameter of a cylinder. The zero of the Vernier scale is observed between 4.20 cm and 4.25 cm on the main scale. The Vernier scale consists of 50 divisions, which are equivalent to 2.45 cm. The 11th division on the Vernier scale coincides exactly with one of the divisions on the main scale. What is the diameter of the cylinder?

Solution:

To find the diameter, we consider the following information: 

• Smallest division on the main scale = 0.05 cm (4.25 – 4.20)
• Main scale reading = 4.20 cm, 
• Vernier coincidence = 24
• Least Count = 0.05 – 2.45/50 = 0.001 cm.

Using these values,

Diameter = Main Scale Reading + (Vernier Coincidence × Least Count) 

Diameter = 4.20 + 11 × 0.001 

Diameter = 4.211 cm

Thus, the diameter of the cylinder is 4.211 cm

Example 2: A Vernier Calliper is used to measure the diameter of a cylinder. The main scale of the Calliper is calibrated in millimeters, and it is observed that 15 divisions on the main scale are equal in length to 20 divisions on the Vernier scale. When measuring the diameter, the main scale reading is 45 divisions, and the 8th division on the Vernier scale coincides with a division on the main scale. Find the least count of the vernier Calliper and the radius of the cylinder.

Solution:

(i) To Determine the Least Count:

MSD (Main Scale Division) = 0.1 cm

20 VSD (Vernier Scale Division) = 15 MSD

Therefore, 

VSD = (19/20) MSD = (15/20) × 0.1 cm = 0.075 cm

Least Count = MSD – VSD 

Least Count = 0.1 cm – 0.075 cm 

Least Count = 0.025 cm

Thus, the least count of the vernier Calliper is 0.025 cm.

(ii) To Find the Radius:

Main Scale Reading = 45 mm = 4.5 cm

Diameter = Main scale reading + (vernier coincidence × least count) 

Diameter = 4.5 cm + (8 × 0.025 cm)

Diameter  = 4.5 cm + 0.2 cm 

Diameter  = 4.7 cm

Radius = Diameter/2 = 4.7/2 = 2.35 cm

Thus, the radius of cylinder is 2.35 cm

FAQs on Vernier Callipers

Q1: What is a Vernier Calliper?

A vernier Calliper is a measuring instrument used to measure the dimensions of an object with high precision. It consists of a main scale and a sliding vernier scale, which allows for more accurate measurements than a regular ruler.

Q2: How does a Vernier Calliper Work?

A vernier Calliper works on the principle of Vernier scale, which provides finer measurement readings. The main scale measures whole units, while the vernier scale slides along the main scale and provides additional fractional readings.

Q3: What are Parts of a Vernier Calliper?

A vernier Calliper consists of several parts: the main scale, vernier scale, jaws for measuring outer dimensions, and depth gauge for measuring depths. It also includes a locking screw to hold measurements in place.

Q4: How to Read Measurements on a Vernier Calliper?

To read measurements on a vernier Calliper, align the object between the jaws and read the main scale reading at the zero mark of the vernier scale. Then, identify the graduation line on the vernier scale that perfectly aligns with a graduation line on the main scale. The value indicated by the aligned lines on the vernier scale represents the fractional part of the measurement.

Q5: What are Applications of Vernier Callipers?

Vernier Callipers are used in various fields, including engineering, manufacturing, and science, where precise measurements are required. They are commonly used for measuring dimensions of objects, thickness, inner and outer diameters, as well as depth measurements.

Q6: How Accurate are Vernier Callipers?

Vernier Callipers are known for their high accuracy. Depending on the quality and design, vernier Callipers can typically measure to the nearest 0.02 mm or even finer.

Q7: What is the function of the vernier calliper?

Vernier calipers accurately measure internal and external dimensions with a minimal reading error of 0.05mm (0.0019 inches), making them superior to flat devices like rulers.