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What is Vernier Caliper? Working and Least count? Learn Here.....!

In this article we will learn about Vernier Caliper. Main parts of Vernier Caliper, working & Precaution. Vernier Caliper is used to measure the internal & external dimension of work piece. So let’s begin our journey towards Vernier Caliper.

What is Vernier Caliper? Working and Least count? Learn Here.....!

What is Vernier Caliper?

A Vernier Caliper is a one of the measurement device which can be used to record an accurate reading between two markings by using mechanical interpolation. Vernier Caliper will increase resolution & reducing measurement error. Vernier Caliper is discovered by Frenchman Pierre  Vernier in 1631. 

Principal of Vernier Caliper

The principal of vernier is based on difference between two division which are nearby but not quite alike for obtaining small difference. It provide the enhancement in accuracy of measurement.

Construction of Vernier Caliper

Image Source : Google | created by tutorialspoint
  • The vernier caliper consist of two scale. one is fixed and other is movable. 
  • The fixed scale is called main scale. it is calibrated on L shape frame and carries a fixed jaw.
  • The movable scale is called vernier scale. it slide over the main scale and carries movable jaw.
  • The movable jaw as well as fixed jaw carries a measurement tip.
  • When the two jaw are closed, the vernier scale coincides with the zero of main scale.
  • An adjustment screw is provided to precise setting of jaws.
  • Locking arrangement is provided to lock the sliding scale on the fixed main scale.
How to use Vernier Caliper

  • Vernier Caliper are employed for both internal and external measurements. 
  • Vernier Caliper is generally used by closing the jaw on work surface and record the reading from main as well as vernier scale.
  • To obtain the Accurate reading, the number of division on main scale is first noted down.
  • The vernier scale is then examined to determine which of its division coincide or most coincide with a division on the main scale.
  • Before using the Vernier Caliper it should be checked for zero error. Ensure that zero line on main scale should coincide with zero line on the vernier scale.
  • Record the reading in mm on main scale to the left of zero on sliding scale.
  • Count the number of division on the vernier scale from zero to a line which exactly coincides with any line on main scale.
Image Source : Google | created by tutorialspoint
  • From the above Figure we observe that 21th division is exactly coinciding with the line on main scale.
  • So the total reading = Main scale reading + the number of division which exactly coincide with the main scale X Least count of vernier Caliper 
  • Thus in our case the total reading in mm = 13 + 21 X 0.02 = 13.42 mm

Vernier Caliper can also be preset to a given measurement for checking the dimension of the component.

Least Count of Vernier Caliper
  • The vernier caliper consist of two scale. one is Main scale and other is Vernier scale. 
  • The main scale is fixed and vernier scale is slide over the main scale.
  • When zero on the main scale coincide with zero on the vernier scale, the vernier scale has one more division than that of the main scale with which it coincide.
  • So we conclude that, the value of one division on vernier scale is smaller than value of one division on main scale. and this difference is nothing but least count.
  • Least count is the difference between value of main scale division and vernier scale division. 
Least Count of Vernier Caliper = Value of smallest division n main scale - The value of the smallest division on vernier scale
  • As we seen from figure, the value of smallest division on main scale  is 1 mm.
  • Figure shows that 50 division of vernier scale coincide  with 49 division on main scale.
  • Therefore the value of one division on vernier scale is 49/50 mm
  • so Least count = 1 - (49/50) = 0.02 mm

Possible Error in Vernier Caliper

  • The error  in the measurement carried out by vernier instrument are usually due to manipulation or miss-handling of the instrument and its jaw on the work piece. The different causes of error are given below.
  • Error due to play between the sliding jaw on the scale.
  • If the sliding jaw frame become worn or warped. It will not able to slide squarely on the main scale and will cause error in measurement.
  • Due to wear and warping of jaw, the zero line on the main scale should not coincide with that of main scale. This is called zero error.
  • Error are also caused by incorrect reading of the vernier scale as the scale is difficult to read even with magnifying glass.
  • Error is also introduced if the measurement line does not match with the line of the scale.
  • Since it is difficult to obtain correct feel due to its size and weight an error may be introduced due to incorrect feel.

Precautions in the use of Vernier Caliper

  • To minimize the error following precaution should be taken while using the instrument.
  • The line of measurement must be coincide the line of scale.
  • While measuring outside diameter with vernier Caliper, the plane of the measurement tip of the caliper must be perpendicular to central lie of the work piece.  The vernier Caliper should not be tilted or twisted.
  • Grip the vernier Caliper near or opposite to the jaw and may by te overhanging projected main bar of caliper.
  • Move the caliper jaw on the work with light touch. Do not apply any extra pressure.
  • The accuracy of measurement primarily depend on two sense i.e. sense of sight& sense of feel. The shortcoming imperfect vision can be overcome by use of corrective eye glass and magnifying glass. The sense of touch is varies from person to person and can be developed with sufficient practice and handling.
  • The measuring instrument must always be properly balanced in hand and held lightly in such a way that only fingers handle the moving and adjusting screw.

This article explained detailed about vernier caliper, working principle, diagram, precaution & possible error. If you find this article useful kindly take few second for us and write in the comment. if you find any wrong information please mention it into comment.

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