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Rulers, Verniers,
Micrometers andMeasurement
UncertaintyReading and understanding
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The ruler
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For an uncertainty of about 1%
a) a ruler, marked in mm, is useful for
making measurements of distances of
about 10cm or greater
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Reading a ruler
".ery measurement is really a subtraction
/-00)cm 2 30 00)cm 4 - 01)cm
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Reading a Vernier
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&ote 10 di.isions on the .ernier scale co.er nine
di.isions on the main scale The .ernier 5orks because of this discre6ancy
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+n this cm scale the reading is 13-cm
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The .ernier 6art of the reading is really a subtraction7
8 4 d 2 d9
8 4 -mm 2 -0:;)mm 4 -0:1)mm
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The le.el of 6recision de6ends on the difference
bet5een the si
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75.0
=hat is the uncertainty>
(mallest measurement on the main scale2 (mallest measurement on the Vernier
1 2 0; 4 01
The reading is 5ritten ?/0 01
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75.5 0.1
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75.7 0.1
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$ifferent Verniers
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=hat 5ill the 6recision of this scale be>
main scale smallest di.ision 4 1mm
.ernier scale smallest di.ision ;@0 mm
1-!9"50 = 1"50 mm = 0.02mm
#ll meas$remen% are %o 0.02mm
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The Micrometer
Reading the micrometer
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"ach mark
here is 4
001mm
Reading 4 .57
mm
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Using the micrometer
$o not o.er tighten the micrometer
$o not store 5ith closed Aa5s
=hen measuring the diameter of a 5ire
take readings across se.eral 6oints at ;0
degrees to each other
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.57mm
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!.07mm
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.22mm
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1.02mm
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.52mm
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10.97mm
10
mm
0?
mm
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Micrometer Uncertainty
The micrometer may not close on
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/3 000mm B 2001) 000mm4.520.01mm
&' %he ero reading as -0.01mm
This reading is .52mm
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$igital micrometers and .ernier
calli6ers The uncertainty of a correctly set digital
micrometer is 10 times less than that of a sim6le
micrometer
(imilarly the uncertainty of digital calli6ers is 10
8 less than that of a sim6le .ernier calli6er
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The digital calli6er
131?mm
on ero
(5itch on and make sure the calli6ers are set in
mm2 blue button
Fully close the cali6er and set the
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The digital micrometer
3-1?
abs
+n@off
set
#bs@inch
unit
C2@D
The uncertainty on this single reading is 0001mm
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The digital micrometer
3-1?
abs
+n@off
set
#bs@inch
unit
C2@D
Using onl* %he ra%che% close the cali6er
Eress the on off button for more than 3 seconds until se%G a66ears
in the 5indo5 abo.e the number The micrometer no5 reads
