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