A Vernier Caliper is a precision measuring instrument used to measure internal and external dimensions, depths, and step measurements with high accuracy. It consists of a main scale and a Vernier scale that allows measurements with greater precision than a regular ruler.
Parts of a Vernier Caliper
The figure 1 above illustrates the following components:
- Main Scale: Fixed ruler-like part with standard metric or imperial markings.
- Vernier Scale: Sliding secondary scale for precise readings.
- Fixed Jaw: Attached to the main scale, used for external measurements.
- Movable Jaw: Slides along the main scale to take measurements.
- Depth Measuring Blade: A thin rod extending from the end for depth measurement.
- Measuring Tips for Internal Diameter: Small upper jaws for internal dimensions.
- Clamping Screw: Locks the sliding jaw in position for accurate readings.
- Guiding Surface: Ensures smooth movement of the Vernier scale.
Working Principle of Vernier Caliper
The working principle of a Vernier Caliper is based on the Vernier Scale, which is a secondary scale that slides over the main scale. The Vernier scale has divisions slightly smaller than those on the main scale, allowing for fractional readings by finding the point where the lines on both scales align.
The Formula for Measurement using a Vernier Caliper:
where:
- Main Scale Reading (MSR): Direct reading from the fixed scale.
- Vernier Scale Reading (VSR): The division of the Vernier scale that aligns exactly with a division of the main scale.
- Least Count (LC): The smallest measurement that can be read using the caliper.
Working of Vernier Caliper
The Vernier Caliper works on the principle of two scales – the main scale and the Vernier scale, which slide over each other to give highly precise measurements. The difference in the division sizes of these two scales allows the user to measure small increments with high accuracy.
Step-by-Step Working of Vernier Caliper:
1. Understanding the Scales:
- Main Scale: A fixed ruler-like scale with standard divisions (in mm or inches).
- Vernier Scale: A sliding secondary scale with divisions slightly smaller than those on the main scale.
2. Measuring an Object:
- External Measurement: Place the object between the fixed and movable jaws.
- Internal Measurement: Use the upper small jaws inside a hollow object.
- Depth Measurement: Extend the depth blade into the object’s hole or cavity.
3. Reading the Measurement:
- Note the Main Scale Reading (MSR)
Identify the last visible division on the main scale before the zero of the Vernier scale. - Note the Vernier Scale Reading (VSR)
Identify which Vernier scale division aligns exactly with any division on the main scale. - Use the Least Count Formula
Multiply the aligned Vernier scale division by the Least Count to get the fractional measurement.
4. Calculating the Final Measurement:
Total Reading=Main Scale Reading+(Vernier Scale Reading×Least Count)
where:
- Main Scale Reading (MSR): Direct reading from the fixed scale.
- Vernier Scale Reading (VSR): The division that aligns exactly.
- Least Count (LC): Smallest measurement increment (e.g., 0.1 mm or 0.02 mm).
Example Calculation:
- Main Scale Reading (MSR) = 4.0 mm
- Vernier Scale Reading (VSR) = 6 (6th division aligns with main scale)
- Least Count (LC) = 0.02 mm
Total Reading=4.0+(6×0.02)=4.12 mm
Thus, the object’s dimension is 4.12 mm.
Types of Vernier Calipers
Vernier calipers come in different types depending on the measurement needs:
| Type | Description |
|---|---|
| Standard Vernier Caliper | Measures internal, external, and depth dimensions with a standard scale. |
| Dial Vernier Caliper | Features a dial indicator for easier reading of measurements. |
| Digital Vernier Caliper | Displays readings digitally for higher accuracy and ease of use. |
| Gear Tooth Vernier Caliper | Specially designed to measure gear teeth thickness accurately. |
| Micrometer Vernier Caliper | Used for highly precise measurements with a micrometer screw. |
Least Count of Vernier Caliper
The Least Count is the smallest value that can be measured accurately with a Vernier caliper.
Formula for Least Count:
\[
\text{Least Count} = \frac{\text{Smallest Division on Main Scale}}{\text{Total Number of Vernier Scale Divisions}}
\]
For a typical Vernier caliper:
- Main Scale Division: 1 mm
- Vernier Scale Divisions: 10
- Least Count = mm = 0.1 mm (or 0.01 cm)
Some high-precision Vernier calipers have Least Count = 0.02 mm.
Advantages of Vernier Calipers
- High Precision: More accurate than a regular ruler.
- Versatile: Measures external, internal, and depth dimensions.
- Easy to Use: Simple to operate with training.
- Durable: Usually made of stainless steel or hardened metal.
- Portable: Compact and easy to carry.
Applications of Vernier Calipers
Vernier calipers are widely used in various fields:
Engineering & Manufacturing:
- Checking dimensions of machine parts.
- Quality control in manufacturing.
- Measuring the thickness of materials.
Science & Research:
- Used in physics and chemistry experiments.
- Measuring specimen dimensions in biology.
Medical & Dentistry:
- Measuring dental structures.
- Precise measurement in orthopedic applications.
Automobile & Aerospace Industry:
- Ensuring accurate dimensions of automotive components.
- Checking engine parts for precision fitting.
Disadvantages of Vernier Calipers
- Manual Errors: Requires skill and careful handling.
- Limited Precision: Not as accurate as a micrometer.
- Wear and Tear: Over time, repeated use may affect accuracy.
- Not Ideal for Large Objects: Limited measuring range.
Conclusion
A Vernier Caliper is a crucial precision instrument used in various fields for accurate measurements. Understanding its working principle, least count, and applications helps in utilizing it effectively for scientific and industrial purposes.