Vernier Caliper Least Count

The vernier caliper least count is the smallest measurement that can be recorded with a vernier caliper. A vernier caliper is a device used for precisely measuring linear dimensions, i.e. a straight line between two points. It is commonly used for measuring smaller objects where accurate measurements are required. A typical use of a vernier caliper is to measure the diameter of a sphere as the jaws of the device can be locked onto each side of the sphere. It is an extremely useful and versatile tool.


What is Vernier Least Count?

The smallest measurement that can be recorded with a vernier caliper is referred to as the least count, also known as the vernier constant. A vernier caliper can measure diameter, radius, length, etc. to 1/10mm (0.1mm or 0.01cm), which is the least count. This is typically used by professionals like lathe mechanics to manufacture certain parts. Vernier Calipers feature two scales, the vernier scale and main scale. The main scale is measured along the main component of the calipers and is divided into centimeters, while the Vernier scale travels over the main scale and is divided up gradually (which is less than millimeters).

How Do You Calculate the Least Count?

A Vernier caliper’s least count is calculated by dividing the very smallest measurement on the main scale by the total divisions of the Vernier Scale. There is also a formula that can be used to calculate the least count on the calipers. It is simply the Vernier caliper’s least count = Main scale’s smallest reading / Number of divisions on the Vernier scale

Zero Error

When a Vernier caliper is fully closed, the zero marker on the Vernier scale must exactly match up with the main scale. If this is not the case, then the Vernier caliper is said to have an error referred to as zero error. This can either be a positive or negative error.

Positive Zero Error

Positive zero error is when the zero on the Vernier scale is too far right on the main scale. As this is a positive error, the resulting zero correction is negative.

Negative Zero Error

Similar to positive zero error, there will be negative zero error if the zero marker on the Vernier scale is too far left on the main scale. Again, since the error is negative, the resulting zero correction is positive.

How To Read a Vernier Caliper

There are a few general steps that can be adhered to to ensure that a Vernier caliper is used correctly:

  • Make sure to calculate/find the least count
  • Close the Vernier caliper completely to analyse if there is any zero error
  • Use the formula for the zero error if needed
  • Hold the object in question between the jaws of the Vernier caliper
  • Tighten the jaws around the object gently
  • The main scale will be on the left of, or coinciding with the Vernier scale zero
  • Measure the main scale reading
  • Use X = ( n x LC) to find the Vernier scale reading

X = Fraction of main scale reading

n = Vernier division where it coincides with main scale

LC = Least count



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