Operation for Reading a vernier caliper
The vernier caliper is an instrument used to make accurate measurements as small as 1/10 millimeter or 1/128 inch. In food science the vernier caliper's uses include measuring for volume and measuring for variation in size of products.
Procedure: The vernier caliper is equipped with jaws or calipers for measuring inside and outside dimensions. A sliding bar is used to measure depth. The main scale is like a ruler in centimeters and inches. The vernier scale is rolled into position for measuring as the jaws clamp the object to be measured. At this point one chooses either to read the inch or the centimeter scale; and the vernier caliper can be read.
Operation for Reading is As Follows:
Read the whole number on the main scale to the left of the zero mark. Place a decimal after this number (A.)
Read the number closest to the left of the vernier. Write this number in the first place after the decimal (A.B).
Find the line where the vernier and main scale come together to make one line. Count the number of vernier marks it took to make this match. Write this number in the second place after the decimal (A.BC).
Numerical figures are substituted in the A.BC positions.
This representation and sample shows this. On the centimeter scale the vernier scale has 10 divisions in the same amount of space that the main scale has 9. Each vernier division is 9/10 mm, or 1/10 mm shorter than the main scale division. These 1/10 millimeters are added (in part C. of operations for reading) to the point that the vernier forms a single line with the main scale. Thus measurements to the nearest 1/10 mm can be made.
On the inch scale the vernier scale has 8 divisions in the same amount of space that the main scale has 7. Seven divisions on the main scale equal 1/2 inch. Each division on the main scale is 1/16 inch. So, 8 divisions equal 8/16 or 1/2 inch. Eight divisions on the vernier equal 7/16 inch. Thus, each vernier division equals 1/16 divided by 8 or 7/128 inches.
Compare this to each division on the main scale. Each main scale division is 1/16 or 6/128. The difference between the vernier and main scale divisions is 1/128 inch. These 1/128 inches are added (in part "C." of operations for reading) to the point that the vernier forms a single line with the main scale. Thus, measurements to the nearest 1/128 inch can be made.