# Vernier Caliper & Micrometer: Mr.Randall's Sig Fig Advice

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• pgoel
In summary, Mr. Randall recommends getting at least 2 significant figures for lengths smaller than 1 cm using instruments like the vernier caliper and micrometer. For lengths between 1 cm and 9.99 cm, you should get 3 significant figures. The Vernier scale digit takes the place of the uncertain digit. While some suggest guessing the 1000th digit when the Vernier scale line falls between marks, this is not necessary for values below the 0.01 place. However, the micrometer caliper scale allows for guessing at the 0.001 mm level, so a measurement of 1.23 cm on a Vernier scale may read as 12.345 mm on the micrometer caliper
pgoel
I asked Mr. Randall about sig figs for this lab, especially on instruments like the vernier caliper and micrometer. This was his answer:

"For lengths smaller than 1 cm, you should get at least 2 sigs: 0.??. (To the 100th place, 0.01.)

Between 1 cm and 9.99 cm, you should get 3: ?.??

The Vernier scale digit takes the place of your “uncertain” digit. I’ve read articles that suggest if the Vernier scale line manages to fall between marks, readers are allowed to guess the 1000th digit, but I’ve never noticed that situation on a scale so small. I’m not expecting any values below the 0.01 place.

But the micrometer caliper scale can give you guessing capability at the 0.001 mm level, so 1.23 cm on a Vernier scale might read as 12.345 mm on the micrometer caliper."

I hope this helps anyone struggling as I was!

Welcome to PF!

Thanks for the tip.

Thanks for posting this ... it's something I might add to the next lab manual revision. :)

## 1. What is a Vernier Caliper?

A Vernier Caliper is a precision measuring tool used to measure distances with high accuracy, typically up to 0.001 inches. It consists of two jaws, one fixed and one movable, and a Vernier scale which allows for more precise readings.

## 2. How do you use a Vernier Caliper?

To use a Vernier Caliper, you first need to ensure that it is clean and free of any debris. Then, open the jaws and place the object you want to measure between them. Close the jaws until they are in contact with the object, and read the measurement on the Vernier scale. You can also use the depth rod to measure the depth of an object.

## 3. What is a Micrometer?

A Micrometer, also known as a micrometer screw gauge, is a precision measuring tool used to measure distances with even higher accuracy, typically up to 0.0001 inches. It consists of a stationary anvil, a movable spindle, and a thimble with a scale that allows for precise readings.

## 4. How do you use a Micrometer?

To use a Micrometer, first make sure it is clean and calibrated. Then, place the object you want to measure between the anvil and the spindle. Turn the thimble until the spindle makes contact with the object. Read the measurement on the scale, and use the Vernier scale if necessary for more precise readings.

## 5. What is the significance of Mr. Randall's Sig Fig Advice when using these tools?

Mr. Randall's Sig Fig Advice reminds us to consider the precision of our measurements and report them appropriately. The number of significant figures used in a measurement should reflect the accuracy of the measuring tool. For example, if a Vernier Caliper measures to 0.001 inches, the measurement should be reported to three significant figures. This helps to ensure that our measurements are accurate and consistent.

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