A quick guide on how to read a vernier caliper. You need to remember two things before we start. E.g. For a measurement reading of 2.13 cm:
The main scale contributes the main number and one decimal place to the reading (2.1 cm)The vernier scale contributes the second decimal place to the reading (0.03 cm)
Check out the image above. We will just use a two steps method to get the measurement 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 cmTo 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, we will add the main scale reading and vernier scale reading together. This will give 2.13 cm.
To ensure that you understand the above steps, let?s go through another example.
Main scale reading: 10.0 cm
Vernier scale reading: 0.02 cm
Measurement: 10.02 cm
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.
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 ALLmeasurements 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 fromALL 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.
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