Measuring the diameter of a circle using a Vernier caliper involves carefully placing the object between the caliper's jaws and reading two main scales to determine the precise size.
A Vernier caliper is a precision instrument used to measure linear dimensions, such as internal and external diameters, depths, and lengths, with high accuracy. It consists of a main scale and a sliding Vernier scale that allows for readings beyond the smallest division on the main scale.
Steps to Measure Diameter
Follow these steps to accurately measure the diameter of a circular object like a sphere or cylinder using the external jaws of a Vernier caliper:
- Prepare the Object: Ensure the circular object is clean and free from any debris that could affect the measurement.
- Open the Jaws: Open the external measuring jaws of the Vernier caliper wide enough to fit the object inside.
- Place the Object: Gently place the circular object between the external jaws. For accurate diameter measurement, ensure the jaws are positioned across the widest part of the circle.
- Close the Jaws: Carefully slide the movable jaw until both jaws firmly but gently touch the opposite sides of the circle. Do not apply excessive force, as this can deform the object or the caliper jaws, leading to inaccurate readings.
- Secure the Measurement: Use the locking screw or lever (if available) to fix the position of the movable jaw. This prevents accidental movement while you read the measurement.
- Remove the Object: Once the jaws are locked, you can remove the object to read the caliper conveniently.
Reading the Vernier Caliper
Reading a Vernier caliper involves combining readings from the main scale and the Vernier scale. As highlighted in the referenced video, there are two different kinds of readings involved: the main scale reading and the Vernier scale reading.
Here's how to obtain the total measurement:
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Determine the Main Scale Reading (MSR): Look at the main scale and find the last full division before the zero mark on the Vernier scale. This is your Main Scale Reading. Read the value on the main scale up to this point.
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Determine the Vernier Scale Reading (VSR): Look at the Vernier scale and find which division mark on the Vernier scale exactly coincides with any division mark on the main scale. The number of this coinciding Vernier scale division (from the Vernier scale's zero mark) is your Vernier Scale Reading number.
- The referenced video mentions an example where the "vernier scale. Reading" is "0.02 centimeter". This value is obtained by multiplying the VSR number by the Vernier caliper's Least Count (LC).
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Determine the Least Count (LC): The Least Count is the smallest measurement that can be made with the caliper. It is usually marked on the instrument or can be calculated. It is the difference between the smallest division on the main scale and the smallest division on the Vernier scale. A common LC for metric Vernier calipers is 0.01 mm or 0.02 mm (which is 0.001 cm or 0.002 cm). The reference's mention of "0.02 centimeter" as a Vernier scale reading suggests the VSR value in that specific example was obtained with a particular VSR number and LC.
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Calculate the Total Diameter: The total diameter is the sum of the Main Scale Reading and the calculated value from the Vernier Scale Reading.
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Total Diameter = Main Scale Reading (MSR) + (Vernier Scale Reading Number × Least Count (LC))
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Using the terminology from the reference, you can think of the total reading as the Main Scale Reading plus the Vernier Scale Reading value (which is the VSR number multiplied by the LC):
Total Diameter = Main Scale Reading (MSR) + Vernier Scale Reading Value -
For example, if the MSR is 2.5 cm, the VSR number is 4, and the LC is 0.01 cm (0.1 mm), the VSR value is 4 * 0.01 cm = 0.04 cm. The total diameter would be 2.5 cm + 0.04 cm = 2.54 cm.
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Measurement Summary Table
Here’s a summary of the readings needed:
| Reading Component | Source Scale | How to Find | Contribution to Total Reading | Example Value (Conceptual) |
|---|---|---|---|---|
| Main Scale Reading (MSR) | Main Scale | Last full division on main scale before the Vernier scale zero. | Direct value from main scale. | 2.5 cm |
| Vernier Scale Reading (VSR) | Vernier Scale | The number of the Vernier division line that coincides with a main scale line. | VSR Number × Least Count (LC) | 0.04 cm (if VSR=4, LC=0.01 cm) |
| Total Diameter | Both Scales | MSR + (VSR Number × LC) OR MSR + VSR Value | Combined reading for precise measurement. | 2.54 cm |
Note: The reference mentions "0.02 centimeter is known as a vernier scale. Reading." This would correspond to the 'Vernier Scale Reading Value' in the table above for that specific measurement example.
Practical Tips
- Always check the zero error of the Vernier caliper before taking a measurement. If the zero mark on the Vernier scale does not align perfectly with the zero mark on the main scale when the jaws are closed, you'll need to correct your final reading.
- Ensure the object is seated correctly between the jaws for a true diameter measurement, especially for irregular or non-spherical objects.
- Practice reading the scale to improve accuracy and speed.
Using a Vernier caliper allows for significantly more precise diameter measurements than a standard ruler.
