The document discusses how to read micrometers and vernier calipers, including determining zero error for micrometers. It explains that if the zero marking on the thimble is above the datum line, there is a negative zero error equal to the number of divisions between the markings times 0.01mm, and if below, there is a positive zero error equal to the thimble reading in millimeters. Readings taken on micrometers must subtract the determined zero error.

1. Reading Micrometer and Vernier Calipers

2. Micrometer

5. Zero Error for Micrometer No zero error

6. This micrometer has zero error. T h e zero marking on the thimble is below t he datum line. So this micrometer h as a positive zero error. How do we count the zero error? In this case we will take the reading on the thimble. Thimble reading = 0.03 mm So the micrometer has a zero error of +0.03 mm. Whatever reading we take on this micrometer we would have to subtract +0.03 mm

7. T h e zero marking on the thimble is above t he datum line. So this micrometer h as a negative zero error. In this case we will have to count the number of divisions on the thimble between the zero marking and the datum line. No. of divisions = 3 Measurement of each division = 0.01mm So the micrometer has a zero error of -0.03 mm. Whatever reading we take on this micrometer we would have to subtract -0.03 mm

8. Vernier Calipers