Vernier Caliper Least Count: Calculate with Formula


What is least count?

Least count of an instrument is the size generally mentioned in millimeter (Denoted by 'mm', is used to indicate the measurement of length in metric form) indicating the smallest division on a scale.

This value is nothing but the smallest size that can be measured using that instrument. This value decides how precise the instrument is.

For example, least count of Vernier Caliper is 0.02 mm and that of Micrometer is 0.01 mm. So, the micrometer is more precise here. Watch video given below.


How to calculate it?

The reading formula for calculation is universal. It can be written as below,

Least Count = Minimum size that can be measured with the main scale alone (MSD) / The total number of divisions on vernier or circular scale (VSD).

Thus, in short-form, it can be written as,
L.C. = MSD / VSD

For Vernier Caliper,

There are two scales viz. Vernier scale & main scale. The main scale is graduated in cm at bottom and in inches at the top while vernier scale just slides along these lines.

If minimum main scale division size is 1mm and there are 50 divisions of the vernier scale, least count value of  Vernier Calliper is 1/50 = 0.02 mm that is equal to 0.002 cm.

If minimum main scale division size is 1mm and there are 10 divisions of the vernier scale, least count value of  Vernier Calliper is 1/10 = 0.1 mm which is equivalent to 0.01 cm.

For Micrometer,

There are two scales viz. circular and main.
There are 50 divisions on the circular scale and minimum division on the main scale counts 0.5mm. We can calculate by the above formula least count of micrometer screw gauge = 0.5/50 = 0.01 mm.

Read: What is Electrical Contactor? How Does a Contactor Work?

what is the least count of micrometer screw gauge?
Micrometer screw gauge

Least count of vernier calipers in inches

Fill-in values in above formula,
L.C. = 0.1 / 40Thus, least count is 0.025 inches.
for a different number of divisions on vernier scale the above value changes accordingly.

To read: Knurling process: Introduction

So, friends, can you now tell me what will be the dial gauge least count?

Vernier caliper parts and functions

Vernier Caliper Least count
Diagram
  • Fix Jaw: The jaw attaches to the main scale at the leftmost end. It is also used as base support while measuring depth.
  • Movable Jaw: The jaw is attached to vernier scale. It can slide and adjust to the job length.
  • Nibs: Using nibs we can measure any internal dimensions. Out of them, one will be fixed and other movable.
  • Screw: Screws are used for locking the movable jaw. 

Uses and applications

Below are the functions of vernier which proves its importance.
  • It can be used to find outside dimensions using fixed and movable jaws.
  • It can also be used in the measurement of inside dimensions using nibs.
  • It can measure depth. The strip is used for this type of measurement.

Zero error

If the zeroth division on the main scale does not match with the zeroth division on a vernier/circular scale then there is said to be zero error.

Zero error may be positive or negative depending on the relative positions of scales.

If the zero of the Vernier scale is to the left of the zero of the main scale then the error is negative and vice-versa.

How to read a vernier caliper in mm

  1. Slide movable jaw on the main scale and rest on both ends of the part to take the measurement.
  2. Now, rotate the fine adjusting screw slowly for more accuracy.
  3. Use the screw to lock the movable jaw.
  4. Now read main scale reading, just before the zeroth division of the vernier scale.
  5. Now find out the vernier scale division, which just coincides with any main scale division. 1 division of Vernier scale = 0.02mm, i.e. 20 Microns
  6. Add main scale & vernier scale reading. This is your final measured dimension on Vernier Caliper.




Vernier Caliper Least Count: Calculate with Formula Vernier Caliper Least Count: Calculate with Formula Reviewed by Vishwanath Nayak on February 09, 2017 Rating: 5

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