1234Introduction of vernier-calliper.ppt

Intro of Vernier Caliper

1. Vernier Caliper

2. Introduction to
Vernier Caliper
IntroductiontoVernierCaliper.Themainuse
ofVerniercalipersistomeasuretheinternal
andexternaldimensionsordistances
accurately.Verniercalipersarepreferredover
otherflatdevices,suchasrulers,astheyhave
anextremelysmallreadingerrorof0.05mm,
whichisaround0.0019inches.

3. Main Scale
Vernier (auxiliary) Scale
Why??

4. Parts of Vernier Caliper

6. General Concept of Least Count

7. Youwillnoticethatoneofthevernierscale
divisionscoincideswithoneofthemainscale
divisions.

8. Principle of Vernier
Ndivisionsonthevernier
scaleisequalto
(N-1)divisionsonthe
mainscale.

9. LeastCountindicatesthedegreeofPrecisionof
measurementthatcanbeachievedbythemeasuring
instrument.
Suppose,Twodifferentverniercallipershavedifferentnumberofequal
divisionsontheirvernierscales
i)10equaldivisionsii)50equaldivisions.
Whichcanmeasuremoreprecisely?
TheleastcountoftheIverniercallipers=1/10=0.1mm
TheleastcountoftheIIverniercallipers=1/50=0.02mm.
Thatis,theIIverniercalliperswith0.02mmofL.Ccanmeasureupto
0.02mmaccurately.
Hence,theprecisionofIIverniercallipersinmorethanIverniercallipers.

10. Question:What happens if instead if N-1 divisions, the N divisions of my
vernier callipers divides N-2 or N-3 divisions on the main scale? Is it
possible? what changes should we make to find the least count? which
calliper would be more precise?
Ans:if (n-2) M.S.D = n V.S.D
Then 1 V.S.D = {(n-2)/n} M.S.D
L.C = 1 M.S.D –1 V.S.D = 1mm –{(n-2)/n} mm = 2/n if n =10
L.C = 2/10 = 0.2 mm
i.e. when (n-1) divisions are changed to (n-2)divisions least count is
increased from 0.1mm to 0.2mm
i.e. the precision of the vernier callipers is decreased.
so, if (n-3) M.S.D s are divided in to n equal divisions on vernier scale
the L.C further increases and the precision further decreases.

11. Principle of Vernier
Thereadingonthemainscalejustbefore(LEFT)thezeroofthevernierisnoted.
ThisiscalledMainscalereading(M.S.R).Thenumberofdivision(n)onthevernier
whichcoincidesperfectlywithanyoneofthemainscaledivisionsisnoted.Thisis
calledverniercoincidence(V.C).Theverniercoincidence(V.C=n)ismultipliedby
leastcounttogetthefractionofamainscaledivision.Thisisaddedtothemain
scalereading(M.S.R)
Readingoftheinstrument=MSR+(nxL.C.)

12. Readingoftheinstrument=MSR+(nxL.C.)

13. Main Scale reading = 1.2 cm;
vernier scale reading = 3×0.01 cm = 0.03 cm
So,
Reading = 1.2 + 0.03 = 1.23 cm
HowtotakereadingofaVernierscale
1 cm

14. Another Example

15. Another Example
2.4cm

16. Another Example

20. Click on the picture for Video on Vernier Scale

21. http://members.shaw.ca/ron.blond/Vern.APPLET
Java Applet for Vernier Scale
Tutor Vista animation

22. No zero error. Positive zero error
Zero Error
Whenjawsoftheverniercallipersareincontact,andifthe
zerodivisionofmainscaledoesnotcoincidewiththezero
markonvernierscale,suchverniercaliperswillhavezero
error.
TypesofZeroErrorinverniercallipers
i)NegativeZeroerror ii)PositiveZeroerror

24. Positivezeroerror:Whenthejawsoftheverniercallipersareclosed,
andifthezeromarkontheauxiliary(vernier)scaleliestotherightofthe
mainscalezero-mark,thenerroriscalledPositiveZeroerror.So,thezero
correctionshouldbesubtractedfromthereadingwhichismeasured.
Zero error = +0.01 cm
Zero error = +0.04 cm

25. whenthejawsareclosedandifthereadingis0.10mm,thezeroerroris
referredtoas+0.10mm.
'actual reading = main scale + vernier scale -(zero error)'
thustheactualreadingis19.00+0.54-(0.10)=19.44mm

26. Negativezeroerror:Whenthejawsoftheverniercallipersareincontact,andifthe
firstmarkontheauxiliary(vernier)scaleliestotheleftofzeroofmainscalesuchan
erroriscalledNegativeZeroerror.So,thezerocorrectionshouldbeaddedtothe
readingwhichismeasured.
Zero error = -0.02 cm
Zero error = -0.08 cm

27. whenthejawsareclosedandifthereadingis-0.08mm,thezeroerroris
referredtoas-0.08mm
'actual reading = main scale + vernier scale -(zero error)'
thustheactualreadingis19.00+0.36-(-0.08)=19.44mm