螺旋測微器和游標(biāo)卡尺的原理及使用方法

2-1MeasurementsMeasuringlengthswithmeterrulePrecision:1millimeterMeasuringlengthswithtapePrecision:1millimeterCorrectway

to

readthe

scale

on

a

rulerPositioneye

perpendicularly

atthemark

onthescale

to

avoids

parallax

errors(視差)Another

reason

forerror:

object

not

alignMeasuringlengthswithmetrerule

2-1Measurements

2-1MeasurementsMeasuringlengthsVerniercalipersMicrometerscrewgaugeThestructureThemechanism:howitworks?Themethod:howtouseit?

2-1MeasurementsVerniercalipersThestructureoftheVerniercaliper

2-1Measurements0Howitworks

2-1Measurements

21mm+0.1mm*3=21.3mm

2.1cm+0.01*3cm=2.13cm20mm+3*0.05mm=20.15mm2.0cm+0.01*1.5cm=2.0+0.015cm=2.015cm1mm+33*0.02mm=1.66mm

0.1cm+0.01*6.6cm=0.1cm+0.066cm=0.166cmMainscale9mm19mm49mmVernierscale10divisions20divisions50divisionsPrecision1/10mm=0.1mm1/20mm=0.05mm1/50mm=0.02mm21mm+3*0.1mm=21.3mm=2.13cm2.1cm+0.01*3cm=2.13cm20mm+3*0.05mm=20.15mm2.0cm+0.01*1.5cm=2.0+0.015cm=2.015cm1mm+0.02*33mm=1.66mm0.1cm+0.01*6.6cm=0.166cmCorrectReading:10.6mm?(+0.3mm)=10.3mm1.06cm-0.03cm=1.03cm

Zeroerror（零位誤差）：+0.3mmnoobject：0.1mm*3=0.3mm0.0cm+0.01*3cm=0.03cmmeasureanobject：10mm+0.1mm*6=10.6mm1.0cm+0.01*6=1.06cmNoobject,Closethecaliperssothatthejawstouchlightlybutfirmlywitheachother.

2-1MeasurementsCorrectReading:0.6mm?(?0.3mm)=0.9mmZeroError

=-0.1mm*（-3）=?0.3mmZeroerrorItisnegative.noobjectmeasureanobject：0mm+0.1mm*6=0.6mmNotice

2-1MeasurementsCheckzeroerror.Closethecaliperssothatthejawstouchlightlybutfirmlywitheachother.

Closethecaliperssothatthejawstouchlightlybutfirmlyonthesidesoftheobjectbeingmeasured.Lookatthezeroonthevernierscale.Readthemainscale,justtotheleftofthezero.Thistellsyouthelengthinmillimetres.Thenlookatthevernierscale.Findthepointwhereoneofitsmarkingsisexactlyalignedwithoneofthemarkingsonthemainscale.Readthevalueonthevernierscale.Thistellsyouthefractionalofamillimetrethatyoumustaddtothemainscalereading.Howtoreadaverniercaliper?

2-1MeasurementsExperiment:VerniercaliperObjective:PracticetheuseofVerniercaliperRequirement:Summarizehowitworksandhowtoreadit(withzeroerror)ExperimentdatarecordingandanalysisApparatusneededMeasuringthethicknessofahollowcylinderMeasuringthevolumeofaglassballDesignyourownexperiment2studentsagroup,10minutesintotalEveryoneshouldusetheVerniercaliperbyhimself/herselfTheexperimentalreportispartofhomeworkNotice:howtoreducethemeasuringerror?

2-1MeasurementsImprovingprecisioninmeasurementsMicrometerscrewgaugeThestructureThemechanism:howitworks?Themethod:howtouseit?

2-1MeasurementsMicrometerscrewgaugeThestructure

2-1MeasurementsMicrometerScrewGaugeTo

measure

diameter

offinewires,

thickness

ofpaper

and

small

lengths,

a

micrometerscrewgaugeis

usedThemicrometer

has

twoscales:Mainscale

on

the

sleeveCircular

scale

on

the

thimbleThereare

50

divisions

onthe

thimbleOnecomplete

turnof

thethimble

moves

thespindle

by0.50

mm0.50mm/50=0.01mm

2-1MeasurementsMainscale:accurateto0.5mmFractionalscale:50divisions,onecompleteturn0.50mm,accurateto0.01mmTrytosummarizebyyourself:howtoreadthemicrometerscrewgauge?

2-1Measurements1.

Readthescaleonthesleeve.Theexampleclearlyshows12mmdivisions.2.

Stillreadingthescaleonthesleeve,afurther

?

mm(0.5)measurementcanbeseenonthebottomhalfofthescale.Themeasurementnowreads12.5mm.3.

Finally,thethimblescaleshows16fulldivisions(thesearehundredthsofamm). Thefinalmeasurementis12.5mm+0.16mm=12.66mmSleevereadsfullmm=12mmSleevereads1/2mm=0.5mmThimblereads=16*0.01mm=0.16mmTotalmeasurement=12.66mm

2-1MeasurementsCheckzeroerrorTurnthebarreluntilthejawsjusttightenontheobject.Usingthefrictionclutchensuresjusttherightpressure.Readthemainscaletothenearest0.5mmReadtheadditionalfractionofamillimeterfromthefractionalscaleHowtoreadamicrometerscrewgauge?Activity

2-1MeasurementsMicrometerscrewgaugeHowtodealwithzeroerror?

2-1MeasurementsPrecautionswhenusingamicrometerNever

tighten

thimble

toomuchClean

theends

of

the

anvil

and

spindle

beforemakinga

measurementAny

dirt

oneither

of

surfaces

could

affect

the

readingCheck

forzeroerror

by

closing

themicrometerwhenthere

is

nothing

between

theanvil

andspindleThe

reading

should

be

zero,

but

itis

common

to

find

asmall

zero

error–Correct

zero

error

by

adjusting

the

final

measurement

2-1Measu