How To Read A Vernier Caliper


vernier caliper

A quick guide on how to read a vernier caliper. A vernier caliper outputs measurement readings in centimetres (cm) and it is precise up to 2 decimal places (E.g. 1.23 cm).

Note: The measurement-reading technique described in this post will be similar for vernier calipers which output measurement readings in inches.


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Measurement Reading Technique For Vernier Caliper

In order to read the measurement readings from vernier caliper properly, you need to remember two things before we start. For example, if a vernier caliper output a measurement reading of 2.13 cm, this means that:

  • The main scale contributes the main number(s) and one decimal place to the reading (E.g. 2.1 cm, whereby 2 is the main number and 0.1 is the one decimal place number)
  • The vernier scale contributes the second decimal place to the reading (E.g. 0.03 cm)
caliper 1

Let’s examine the image of the vernier caliper readings above. We will just use a two steps method to get the measurement reading from this:

  • To obtain the main scale reading: Look at the image above, 2.1 cm is to the immediate left of the zero on the vernier scale. Hence, the main scale reading is 2.1 cm
  • To obtain the vernier scale reading: Look at the image above and look closely for an alignment of the scale lines of the main scale and vernier scale. In the image above, the aligned line correspond to 3. Hence, the vernier scale reading is 0.03 cm.

In order to obtain the final measurement reading, we will add the main scale reading and vernier scale reading together. This will give 2.1 cm + 0.03 cm = 2.13 cm.

In a nutshell

Use the following formula:

$$ \text{Obtained reading} = \text{Main scale reading} \, + \, \text{Vernier scale reading} $$

Let’s go through another example to ensure that you understand the above steps:

caliper 2

Main scale reading: 10.0 cm (Immediate left of zero)

Vernier scale reading: 0.02 cm (Alignment of scale lines)

Measurement reading: 10.02 cm

Compensating For Zero Error

In a nutshell

Use the following formula:

$ \text{Correct reading} = \text{Obtained reading} \, – \, \text{Zero error} $

where $\text{zero error}$ can be either negative (the “0” of vernier scale is left of the “0” of the main scale) or positive (the “0” of vernier scale is right of the “0” of the main scale)

Explanation

Now, we shall try with zero error. If you are not familiar on how to handle zero error for vernier calipers, I suggest that you read up on Measurement of Length.

caliper 3

The reading on the top is the measurement obtained and the reading at the bottom is the zero error. Find the actual measurement. (Meaning: get rid of the zero error in the measurement or take into account the zero error)

Measurement with zero error: 3.34 cm

Zero error: – 0.04 cm (negative because the vernier scale is to the left)

Measurement without zero error: $3.34 \, – ( \, – 0.04) = 3.38$ cm

If you do not understand the subtraction of the negative zero error from the measurement, please read on. Since the zero error is -0.04 cm, this means that all measurements taken by the vernier calipers will be SMALLER by 0.04 cm. Hence, you will have to ADD 0.04 cm to ALL measurements in order to get the TRUE measurement. The subtraction is done in the above case is to have an elegant way of obtaining a resultant addition: $3.34 + 0.04 = 3.38$ and to make it COMPATIBLE with positive zero error. This means that once you have determined the nature of the zero error (positive or negative), you can just subtract the zero error and be sure that your final answer is correct.

Consider a zero error of +0.04 cm. With my method, $3.34 \, – (+ 0.04) = 3.30$ cm.

Normal method: Since the zero error is +0.04 cm, this means that all measurements taken by the vernier calipers will be larger by 0.04 cm. Hence, you will have to SUBTRACT 0.04 cm from ALL measurements in order to get the true measurement. The final calculation will be $3.34 \, – 0.04 = 3.30$ cm, which is the same as my method.

Note: I hope that I did not confuse you. Drop a comment below if you encounter any difficulties.


More Vernier Caliper Practice:


Self-Test Questions For Vernier Calipers

Where on the vernier calipers would you read to obtain the main scale reading?

Show/Hide Answer

The main scale reading is obtained from the reading on the main scale that is at the immediate left of the zero on the vernier scale.


Where on the vernier calipers would you read to obtain the vernier scale reading?

Show/Hide Answer

The vernier scale reading is obtained from the reading on the main scale that has an alignment of the scale lines of the main scale and vernier scale.


What is the smallest possible reading (in cm) of a vernier caliper?

Show/Hide Answer

The smallest possible reading of a vernier caliper is 0.01 cm.

If you still do not understand the concept, there is a very useful simulation of the vernier calipers: Vernier Caliper Simulation (Source)


Back To Measurement Of Physical Quantities (O Level)

Back To O Level Topic List


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