Vernier Caliper Measurement || Least Count|| Zero Error Calculation || IIT foundation Physics for class 9

Length Measuring Device || IIT FOUNDATION PHYSICS CLASS 9  

Vernier Caliper

Many devices and Instruments are used to measure various physical quantity. Different instruments are used for measuring length depending upon the length being measured.

For measuring the length of a room, width of a road, length of a piece of cloth, etc., which are larger quantities, measuring tapes may be used.

But while measuring smaller lengths, like the diameter of a rod or wire, the length of a small rod, the thickness of a lamination sheet, etc., more accurate instruments need to be used. Vernier calliper is one such instrument.

Every measuring device has its own accuracy that can be expressed in terms of Least Count.

Least Count 

Least count of an instrument is the smallest measurement that the instrument can measure accurately. The least count of a metre scale is 0.1 cm.

Meter Scale 

• Graduated in millimetres
• Least Count = 1 mm
• Observation should be made without parallax error.

Vernier Caliper

• Used to measure the distance between two opposing sides of an object very precisely
• Consists of two Scale
• Main Scale (fixed)
• Vernier Scale (movable
•  Vernier calliper was invented by  Pierre Vernier

• Main Scale

• consists of a steel metallic strip graduated in centimeters at one edge and in inches at the other edge
• It carries the inner and outer measuring jaws
• When the two jaws are in contact, the zero of the main scale and the zero of the Vernier scale should coincide

• Zero Error

• Jaws are in contact but zeroth division of MS and Zeroth division of VS does not coincide
• It could be positive or Negative

• Positive Zero Error
• When two jaws are in contact, zeroth division of VS is right to the zeroth division of MS
• If n ^th division of VS coincide with some division of MS.
• Error = + ( n x LC )
• Correction = - ( n x LC )

• Negetive Zero Error
• When two jaws are in contact, zeroth division of VS is left to the zeroth division of MS
• If  n ^th  division of VS coincide with some division of MS.
• Error = - ( n x LC )
• Correction = + ( n x LC )

• Vernier Scale
• A vernier scale slides on the strip. 
• It can be fixed in any position by the retainer.
• The principal of Vernier is to make 'N' Vernier Scale Division = (N-1) division of Main Scale
• Generally the standard Vernier scale is provided with 10 gradation to coincide 9 Main Scale Division.
• 10 VSD = 9 mm
• 1 VSD = 0.9 mm
• Outer Measuring Jaws measure object’s outer dimension
• Inner Measuring Jaws measure object’s inner dimension
• The retainer helps to retain the object within the jaws of the Vernier calipers.
• The depth measuring prong helps to measure the depth of an object

• Least Count
• The least count or the smallest reading which you can get with the instrument
• Least Count = 1 Main Scale Division – 1 Vernier Scale Division = 1 mm - 0.9 mm = 0.1 mm = .01 cm

• Procedure for taking measurements using a Vernier Calliper:

• Check the vernier caliper whether zero error exist or not, if exist then check whether it is positive or negetive
• Determine the least count of the given calliper
• Calculate zero error correction
• Make surethat object should be held tightly and gently between the external jaws (for external dimensions) or with internal jaws (for inner dimensions)
• Observe Main Scale Reading (M.S.R.) 
• It is the smaller of the two values of the main scale between which the zero division of vernier scale lies
• Observe Vernier Coinciding Division (V.C.D. or n)
• It is the vernier scale division which coincides with any one of main scale divisions. 
• It is denoted as ‘n’
• Calculate Length of the object
• measurement = M.S.R. + n × L.C + zero error correction

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