Tap to Read ➤

How to Read a Vernier Caliper Accurately

Charlie S May 12, 2019
The vernier caliper is an instrument which we all have heard of, but many of us might not be able to use it very effectively. This piece will help you know how to read a vernier caliper.
Vernier caliper is one of the most famous and widely used instruments for measuring purposes. It's structure is a bit complicated for someone who hasn't seen it before.
However, once you get comfortable with this unique apparatus, you would be able to take measurements of objects quickly and accurately. Before we know how to read a vernier caliper, let us know of its basic structure here.

Structure

The structure of the vernier caliper can be classified into following parts:
  • Vernier readout
  • Caliper locking screw
  • Upper jaws of the caliper
  • Main body
  • Frame of vernier
  • Depth pole of the caliper
  • Outside diameter jaws of the caliper

Facts

  • The purpose of the locking screw is to help the user to fix the vernier on the body
  • The function of the inside diameter jaws is to measure the diameter of insider pipe and width of the grooves
  • Outside diameter jaws help the user measure the outside diameter of the pipes as well as their thickness
  • Depth pole is useful for measuring depth of pipes and grooves
  • Calibration is present on the body as well as the vernier of this apparatus

Reading a Vernier Caliper and Doing Measurements

On a ruler, each marking corresponds to one unit. So, if you move three marks on the right of 0, the reading on the main ruler would be 3.0.
For a vernier caliper with a resolution of 0.1, the minimum scale would be of 1mm and the number of scales would be 10. Therefore, the total length of the scales would be 9mm. From this, the length of every scale comes out to be 0.9mm. We are supposed to move the vernier to the right by 0.1mm when length of the measuring item is 0.1mm.

Measuring

Step: 1

The vernier caliper should be calibrated such that the vernier ruler's zero mark matches the main ruler's main mark exactly.

Step: 2

If this does not happen, then you should adjust the vernier to match the two zeroes by loosening the bolt which connects it to the movable jaw. Once you are done with matching the zeroes, tighten the bolts again.

Step: 3

In case calibrating the caliper is not possible, then you need to remember the error value and add or decrease it after you get the measuring value. If the zero scale of the vernier is on the right of the 0 scale of the body during the measurement, then the error value should be added and if it is one the left, the error value needs to be subtracted.

Step: 4

The object which you wish to measure should have the instrument's jaws around it. Now, your task is to find a mark on the vernier scale that matches the mark on the main scale. Now, counting from the zero mark on the vernier scale, you have to calculate the number of marks on the main scale. This number should be on the right side of the decimal point.

Step: 5

The integer calculation is important too. This calculation, can be done with the following formula:
Integer = (Marks present on the right side of main scale's highest whole number) + (Marks present on the left of the vernier scale's zero mark).
The total length is the summation of the integral value and the decimal value. In this way, you can get the final measurement for the object.

Example

Here is the mathematical method of calculating length with the help of vernier caliper. Let us assume that there are nineteen divisions before zero on the vernier scale (with 50 divisions). So, here the integer part would be 19.
Now, count the divisions till you locate the division which matches to the division on main scale. This will be 32 divisions on the vernier scale. Every division on the vernier scale is of 0.02 mm.
The multiplication of the 32 divisions and 0.02 will give you 0.64 as the decimal part. Now, we know that final answer would be the addition of the integer and decimal parts. So, final measurement = 19 + 0.64 = 19.64 mm.
Sufficient practice and experience of using this instrument will enable us to measure accurate and precise dimensions of any object.