Vernier caliper is an instrument used to measure the length,diameter,radius etc.
It can measure up to 1/10 of mm (or 0.1 mm 0.01 cm) which is called least count of V.C .
There are two scales of V.C
- Vernier scale
- Main scale
Main scale is graduated is centimeter while Vernier scale slides along the main scale and is graduated in division (less than millimeter).
Parts and function of vernier caliper
There are two set of jaws:
- Two jaws
- Main scale
- vernier scale
(1) Lower Jaws:
The lower jaws A and B are used to measure length. Thickness or external diameter of an object.
The upper jaws C and D are used to measure the internal diameter of objects like a hollow cylinder or tube.
The jaws A and B are fixed where B and D are moveable. The moveable jaws are attached to the vernier and they slides along the main scale.
- The smallest reading which can be accurately measured with a vernier caliper is called its least count (L.C),it is also known as vernier constant.It is the difference between one main scale division which is 1 mm and one vernier division which is (0.9) .
L.C = 1 mm – 0.9 mm =0.1 mm
There is another method to find least count which is given as:
Vernier caliper zero error
When the jaws of Vernier calippers are brought into contact, the zero of the Vernier must coincide with the zero of the main scale. Otherwise, the instrument has an error called zero error. Zero error can be negative or positive.
Negative Zero Error
If the zero of the Vernier scale is to the left of the zero of the main scale then the error is negative. Since the zero error is negative, the zero correction will be positive.
Positive zero error
If the zero of the Vernier scale is to the right of the zero of the main scale then the error is positive. Since the zero error is positive, the zero correction will be negative.