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Saturday, 26 November 2011

VERNIER CALIPER

VERNIER CALIPER
Definition: It is an instrument used to measure the distance accurately up to 0.1 mm

Construction:
It consists of a graduated centimeter bar known as main scale with a moveable scale or 10 divisions known as vernier scale. It has two sets of jaws for the measurement of internal and external diameter of cylindrical objects.


VERNIER CONSTANT (V.C.) OR LEAST COUNT (L.C.):
Definition: Vernier constant or the least count is the minimum measurement that can be measured by vernier calipers.

Formula:
Least Count = 1 main scale division - 1 Vernier scale div.
                    = 1 mm - 0.9 mm
                    = 0.1 mm
                    = 0.1/10
                    = 0.01 Cm
   OR

V.C. = Value of one main scale division / Total number of vernier scale divisions
        = 1/110
        = 0.1 mm
        = 0.01cm

ZERO ERROR:
On closing the jaws if the zero of the main scale does not coincide with the zero of the vernier scale then the instrument has zero error.

POSITIVE ZERO ERROR:
On closing the jaws if the zero of the vernier scale is on the right of the main scale then the zero error is positive.

NEGATIVE ZERO ERROR:
On closing the jaws if the zero of the vernier scale is on the left of the main scale then the zero error is negative.

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