ye le Rana Vernier ki detail pori detail Calipers are used to make external or internal measurements. A caliper does not have dial or scale to give direct reading. It is used with a scale to get measurements. 2.2. Vernier Caliper Caliper mechanical device used to determine small lengths with reasonable accuracy. Simple calipers have two movable legs of some desired shape to meet surfaces whose separation is to be measured. The adjusted width between the leg tips is then placed against some length scale. The more complex vernier caliper is wrench like and has a scale that allows direct reading of the adjusted width between the jaws of the wrench. Reading Scales of the Vernier Suppose a ruler has marking every tenth of an inch but it is desired to read accurately to hundredths. A separate scale (fig.2.2) is added to the ruler. It has 10 markings on it that take up the same distance as 9 markings on the ruler scale. Thus, each space on the vernier is 1/10 of 9/10 inch, or 9/100 inch. How much smaller is a 10/100 and the vernier space is 9/100 inch. The vernier space is smaller by the different between these two numbers, as follows: Each vernier space is 1/100 inch smaller than a ruler space. As an example of the use of the vernier scale, suppose that we are measuring the steel bar shown in figure 2.3. The end of the bar almost reaches the 3 inch mark on the ruler and we estimate that it is about halfway between 2.9 inches and 3.0 inches. The vernier marks help us to decide whether the exact measurement is .294 inches, 2.95 inches, or 2.96 inches. The 0 on the vernier scale is spaces the distance of exactly one ruler mark (in this case, one tenth-of an inch) from the left hand end of the vernier. The 1 on the vernier hundredth of an inch closer to alignment than the 0. This is because each space on the vernier is one hundredth of an inch shorter than each space on the ruler. The vernier principle may be used to get fine linear readings, angular readings, etc. The vernier has one more marking than the number of markings on an equal space f the convential scale of the measuring instrument. For example, the vernier caliper (fig. 2.1) has 25 markings on the vernier for 24 on the caliper scale. The caliper is marked off to read to fortieths (0.025) of an inch, and the vernier extends the accuracy to a thousands of an inch.
Posted on: Wed, 06 Nov 2013 15:16:31 +0000
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