A Vernier caliper is an instrument used to measure both external and internal dimensions and distances. It is a device that allows more precise measurements to be taken than conventional ones such as rulers. In addition, it has a margin of error of only 0.05 mm (0.0019 inches). Manual vernier calipers can include both imperial and metric measurements, but it is not uncommon for them to only have one of them.
Steps
Part 1 of 2: Prepare Instruments and Tools
Step 1. Learn about the parts of a Vernier caliper
This device has two main jaws that are used to measure the external diameter, as well as smaller ones that are intended to measure the internal diameter of objects. Also, some models also have a depth gauge. The main scale is fixed while the Vernier scale is one that slides to open and close the jaws.
Step 2. Read the scales that appear on your Vernier caliper
Each scale on the caliper is read like any rule. Typically, the caliper has a main scale that is marked in centimeters or inches, plus smaller divisions between each of them. The sliding scale (Vernier) has an engraved label that indicates what it represents.
- If the sliding scale does not have a label, the numbered divisions most likely represent 1/10 of the smallest division on the main scale. For example, if the smallest lines on the main scale represent 0.1 cm, it means that each division on the Vernier scale will represent 0.01 cm.
- The main scale is the “natural size”, while the sliding scale is an amplification in order to obtain an easier reading. This amplification system allows the Vernier caliber to obtain greater precision than a ruler.
Step 3. Review the scale of the smallest divisions
Before taking a measurement, count the number of lines between two numbers on the Vernier scale. Use this value to determine how much the distance between each of the smaller lines represents.
For example, numbers on a Vernier scale represent 0.1 cm and there are five unnumbered lines between them. 0.1 cm / 5 = 0.02 cm. Therefore, each of the unnumbered lines is equivalent to 0.02
Step 4. Clean the object to be measured
This will ensure that it is fat-free and that nothing will interfere with an accurate measurement.
Step 5. Unscrew the screw
If your Vernier caliper has a security screw, loosen it before you begin.
Turning something to the right (clockwise) will make it tighter, while turning it to the left (counterclockwise) will make it looser
Step 6. Close the jaws of the caliper
Before taking a measurement, close the caliper jaws and zero them to reset the reading so that you can get an accurate measurement. If you don't, the scales will not be aligned at zero when taking a measurement, which you will have to correct to avoid getting an error.
- For example, if the zero on the sliding scale lines up with the 1mm mark on the fixed scale, it means that you have a positive zero error of +1 mm. If you want to get the correct result, subtract 1mm from all measurements made.
- If the zero on the sliding scale is to the left of the one on the main scale, you will have a negative zero error. Therefore, slide it until the zeros are aligned while looking at another mark in order to visualize the size of the error. For example, if the 0.5m mark moves from the 1mm mark to the 2.1mm mark, the zero error is - (21 - 1), or - 1.1mm. To correct this, add 1.1 mm to all measurements.
Part 2 of 2: Using the calibrator
Step 1. Slide one of the jaws against the object
The caliper has two types of jaws: the larger ones fit around an object to measure its length; the smaller ones fit into an opening and then expand to measure the internal diameter. You can adjust any of these jaws by sliding the smaller scale. Once you've placed one of the jaws in the correct position, tighten the set screw (if there is one).
Step 2. Check the main scale, where it lines up with the zero of the sliding scale
Generally, the main scale of a Vernier caliper indicates the whole number plus the first decimal place. Interpret this measurement as you would a ruler, measuring to the zero mark on the sliding scale (Vernier).
- For example, if the 0 on the sliding scale lines up with the 2 cm mark, then the measurement is 2 cm. If the measurement exceeds the 2 cm measurement to the sixth tenth mark, it means that the measurement is 2.6 cm.
- If the result falls between two lines, just use the smaller value. Don't try to calculate a value between the two lines.
Step 3. Read the Vernier scale
On the Vernier scale, look for the first mark that lines up perfectly with any line on the main scale. This mark will indicate the value of the additional digits.
- For example, 14 on the Vernier scale lines up with a line on the major scale. If we assume that the scale represents values that increase by 0.01, the number 14 represents 0.014 cm.
- It doesn't matter which line lines up with which on the main scale. You have already obtained the reading of the main scale, so it is not necessary to obtain another one.
Step 4. Add the numbers
Add the results you got on the main scale and the Vernier scale to get the final answer. Make sure to use the correct units as indicated on each scale or you will not get an accurate answer.
- In the example above, it was obtained 2.6 cm on the main scale and 0.014 cm on the Vernier scale. Therefore, the final measure is 2,614 cm.
- The digits don't always line up in this neat way. For example, if the main scale gives a measurement of 0.85 cm and the Vernier scale indicates 0.012, then the result would be the following: 0.85 + 0.012 = 0.862 cm.