A quick guide on how to read a micrometer screw gauge. Similar to the way a vernier caliper is read, a micrometer reading contains two parts:

- the first part is contributed by the main scale on the sleeve
- the second part is contributed by the rotating vernier scale on the thimble

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## Measurement Reading Technique For Micrometer

The above image shows a typical micrometer screw gauge and how to read it. Steps:

- To obtain the first part of the measurement: Look at the image above, you will see a number 5 to the immediate left of the thimble. This means 5.0 mm. Notice that there is an extra line below the datum line, this represents an additional 0.5 mm. So the first part of the measurement is $5.0 + 0.5 = 5.5$ mm.
- To obtain the second part of the measurement: Look at the image above, the number 28 on the rotating vernier scale coincides with the datum line on the sleeve. Hence, 0.28 mm is the second part of the measurement.

You just have to add the first part and second part of the measurement to obtain the micrometer reading: $5.5 + 0.28 = 5.78$ mm.

To ensure that you understand the steps above, here’s one more example:

First part of the measurement: 2.5 mm

Second part of the measurement: 0.38 mm

Final measurement: 2.88 mm

## 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” marking on the thimble is **above** the datum line) or **positive** ( the “0” marking on the thimble is **below** the datum line )

### Explanation

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

The reading on the bottom is the measurement obtained and the reading at the top 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: 1.76 mm

Zero error: + 0.01 mm (positive because the zero marking on the thimble is below the datum line)

Measurement without zero error: $1.76 \, – (+ 0.01) = 1.75$ mm

The subtraction logic is similar to the method explained in How to read a vernier caliper. You can take a look and comment below, if you encounter any difficulties.

### Self-Test Questions

**What is the smallest possible reading (in mm) on the thimble scale? What is the biggest possible reading?**

**Show/Hide Answer**

The smallest possible reading on the thimble scale is 0.01 mm, while the biggest possible reading is 0.49 mm.

If you still do not understand the concept, there is a **very useful** simulation of the micrometer screw gauge here.

**Bonus:** You can get this micrometer app on your mobile phone (Android): https://www.miniphysics.com/link/micrometerapp

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I have seen this particular question (same picture) about a micrometer in the exam but the answer 2.88 mm was not in the choices. How is that?

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Need some explanation on how to get the zero errors… Thank you.

its usually caused by faulty instruments

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The concept for screw measurement reading explains very well. All of us know that the micrometer screw gauge is a small but very essential measuring device.

where is the least count ? I’m confused

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what is applications of micro meter screw gauge

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but i need to know how to find reading on screw gauge if the zero is above the datum line

plzzz must reply

if zero is above the datum line than the value of will be negative that is 0-the coincided number

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This is in the range of good not in the range of outstanding.

I have to agree. Plenty of proffessional online animations explaining the procedure. This can be improved.

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Get my new Android micrometer app here.

https://play.google.com/store/apps/details?id=com.ionicframework.micrometerapp268865

Enjoy!

Thank you for your contributions to the Physics community. Your link has been added to the main post. 🙂

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please, upload how to calculate readings in cm. They are in mm.

Just convert from mm to cm?

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Here I am again! From vernier calliper to micrometer… Wish me luck in my exam today!!!

After reading it now I can perfectly use a screw guage….Thanks alot

I have created a HTML 5 simulation.

Check it out. It even has a zero error.

Micrometer Model

Enjoy

Wow! Brilliant work!

nice way to explain……..

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I also enjoyed it

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Im a chef btw.

Thanks much I enjoyed it

I still don’t get it please put in more emphasis especially on the reading aspect and also the calculation. i want to know how read the guage well so pictures and teaching programmes

There are plans to expand this post. Please keep a look out for it. 🙂

same is with me

isn`t the second part is measured by multiplying the least count with thimble scale reading?

and so it should be 0.001×38=0.038……….. confused please explain

The least count is 0.01 mm. Hence it is 0.01 mm X 38 = 0.38.

nice…. but i needed smthng else 😉

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Dear sir

You should give some more examples

Thanks

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Thank you very helpful

Agreed*

Since the least count of screw gauge is 0.001cm, the reading must come in same way for example 1.762

but your reading is upto 2 decimal only

All of the readings are in mm.

How can we remove the zero error?

You can “remove” the zero error by using the calculation method above.

Alternatively, you can remove the zero error (permanently) by re-calibrating (re-zero’ing) the micrometer screw gauge by using a micrometer spanner wrench.

In the school setting, zero error in micrometer screw gauge is due to the students’ mis-handling of the micrometer screw gauge. (E.g. Over-tightening of the micrometer screw gauge)

I don’t understand what actually the zero error is. :/

Good and easy to understand. Thank you for your sharing

http://arxiv.org/ftp/arxiv/papers/1408/1408.3803.pdf

feel free to link to my simulations, licensed CC-BY http://creativecommons.org/licenses/by/2.0/