Vernier Caliper
6 Minutes
Vernier caliper guide for students: learn its parts, find the least count, and measure the diameter of an object. An English science lesson.
- Parts like internal jaws, external jaws, and the back metal strip
- Calculating the least count of the vernier caliper as 0.1 mm
- Finding the exact diameter of a biscuit using the two scales
What this lesson teaches
A Vernier caliper is a measuring instrument used to accurately measure lengths, thicknesses, internal and external diameters, and depths smaller than one millimeter. It consists of a regular main scale combined with a sliding vernier scale invented by a French mathematician in 1631.
Parts of a Vernier caliper
- The lower jaws, or external jaws, clamp around an object to measure its outer size or external diameter.
- The upper jaws, or internal jaws, fit inside an opening to measure inner size, such as the internal diameter of a cup.
- The back metal strip slides out from behind the tool to measure the depth of an object.
- The main scale is the standard ruler, while the vernier scale has ten divisions that fit across nine divisions of the main scale.
Finding the least count
The least count is the smallest value an instrument can measure. A normal scale has a least count of one millimeter. For a Vernier caliper, the least count is calculated by dividing the smallest main scale division of one millimeter by the ten divisions on the vernier scale. This gives a least count of 0.1 millimeters, or 0.01 centimeters, allowing measurements to change in steps of 0.1 millimeters instead of whole millimeters.
Steps to take a measurement
- Grip the object between the lower jaws and note where the first line of the vernier scale starts to find the main scale reading.
- Identify the vernier coincidence, which is the exact point where a vernier scale line matches a main scale line.
- Multiply the vernier coincidence number by the least count in centimeters, which is 0.01 centimeters.
- Add this calculated value to the main scale reading to find the final accurate measurement.
Example of measuring a biscuit
To find the diameter of a biscuit, it is placed between the lower jaws. The main scale reading shows 5.7 centimeters, and the vernier coincidence is 4. Multiplying 4 by 0.01 centimeters gives 0.04 centimeters, representing the distance between the last mark of the main scale and the first mark of the vernier scale. Adding 5.7 centimeters and 0.04 centimeters gives a total diameter of 5.74 centimeters, or 57.4 millimeters, whereas a standard ruler would only show 5.7 centimeters.