metrology is science considering measurement -...
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Metrology is science considering measurement
Categories:› Scientific – deals with organization and development
of etalons and their conservation(highest level)
› Industrial – deals with function of measuring devices used in industry in manufacturing and testing processes
› Legal – deals with precision of measurement in situations where the exact measurement is necessary for justice of economic transactions, health and security
Fields of metrology:› Weight
› Electricity
› Length
› Time and frequency
› Thermometry
› Ion radiation and radioactivity
› Volume
› Acoustic measurements
› Etc.
Continuity
Is property of measured value or etalon
value that can express the relation to
reference on national or international
level. This relationship is expressed
through an uninterupted chain of
relationships between components
where the unceratainity is known.
Unit definition
International etalons
National etalons
• Home national etalons
• Foreign national etalons
Reference etalones
Company etalones
Measurement
Etalons are changing with development of
science
Length etalon - meter
1795 – bar made of brass
1799 – bar made of platinum and iridium
1960 - 1 650 763,73 times the wave length of
radiation that is equal to transition of electron
from quantum level 2p10 to level 5d5 in
Cryptonium-86
1983 – distance reached by light in time of
1/299 792 458 second.
Basic procedure for securing the continuity ofmeasurement is the calibration. Calibration isaquiring metrological characteristics ofmeasuring device. This is made by referencingthem to etalones.
Reasons for calibration:
1) To secure that the value measured by thedevice is same as to another device ormethod
2) To secure the measured value is correct
3) To secure the reliability of measuring device.
Direct
› measuring device measures directly the
wanted quantity or property
Indirect
› measuring device measures another
quantity or property from that the wanted
quantity or property can be calculated or
derived
Absolute
› I acquire directly a value of quantity or
property
Comparatory
› I acquire the difference between the etalon
and the measured value only
caliper
micrometer
block gauges
pasameter
microskope
lengthmeter
laserinterferometer
…
CMM (Coordinate measuring machine)
basic comunal device - calliper
precision:
› 0,1; 0,05; 0,02 mm (nonius, Vernier scale)
› 0,01 mm (digital)
range… 150 ÷ 3000 mm
types:
› classical(nonius)
› digital
› with indicator
with nonius (Vernier sc.)
outer dimension
inner dimension
depth
digital
presentation:
display
display + output (RS232, USB)
IP66 – waterproof cover
solar powered
indicator
The most common device:
caliper
precision:
› 0,01; 0,005 (mechanical)
› 0,005 ÷ 0,0001 (digital)
range… (0 ÷ 25) ÷ (900 ÷ 1000) mm
types:
› mechanical
› digital
measurement
outer dim.
inner dim.
depth
special types:
plate
tubes
prizmatic
…
special types:
plate
tubes
prizmatic
tolerances
thread
threetouch
holemicrometer
…
micrometer
www.somex.cz
0 30
20
0 30
20
0
0
00
2,24 2,76
2,51 2,49
indicator gauge
not absolute
measurement
must watch the
„hand“ to see if it
did not run the full
circle
scale division!!!
indicator gauge examples
accuracy (4 grades):
› 0,5 ÷ 0,05 mm (cca 5 mm)
› 8 ÷ 4 mm (cca 1 m)
range … ~ 0,1 ÷ 1000 mm
types:
› steel (~ 800 HV)
› sintered carbide
› ceramic (~ 1350 HV)
properties:
ground, polished, lapped
no surface protection
thin oil film
geometric precision
primary block accuracy
(0,02+0,05 .L [m]) mm
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dimenstions
a set of different dimensions in a box (ex. 32 pcs set)
1,005 mm (1pc)
1,01-1,09 step 0,01 mm (9pcs)
1,1-1,9 mm step 0,1 mm (9pcs)
1-9 mm step 1 mm (9pcs)
10-30 mm step 10 mm (3pcs)
50 mm (1pc)
for specific value = put together parts› Handle with care!!!
Together with a two-axis
table with micrometric
screws it is a universal
measuring device
The ocular includes the
„crosshair“
› Two perpendicular lines
› Three lines rotated 60°
› Four line rotated 45°
› Shape lines (thread profiles)
Universal Length Measuring Machine
Accuracy – 1 ÷ 0,1 mm
Measuring range – up to 6 meters
Laserinterferometer
Accuracy = up to 0,01 mm
(depending on measured
length)
(0,5+1,1.L/1000 ) mm
Range:
very variable
(up to 100 meters)
Angle gauges
Square – for right angle
Protractor
Sine bar
level
Like linear block gauges
For fast measurements in practical life
Mainly 90°
Also 45°, 60°, 120°a 135°
Rotary arm
digital
With moving arm
Rotary arm
digital
With moving arm
With occular
inclinometer
Used with block gauges
Mechanical – hydraulic
Gyroscopic -
Digital - accelerometer
threepin method
gauges
thread snap gauge
microscope
Micrometer
Problem is that the thread si too complex to bemeasured. And also that the diameters are not recognizable on the part
Nominal diameter (Major and minor diameter)
Indirect measurement – we measure the „Diameter over
pins“ and we can calculate from it the nominal diameter
For pitch measurement
Gauge is placed to the thread
Thread snap gauge
Thread plug gauge
List of tasks:
1. Profile projector measurements (-o-)
2. Cylindrical plug gauge control on microindicator (-o-)
3. Cone measurement on a laboratory microscope
4. Angle measurement with an optical bevel
5. Frontal run-out measurement (-o-)
6. Run-out measurement of a rotary part (-o-)
7. Thread measurement using a three wire method
8. Measurement using a laboratory microscope (-o-)
9. Gear measurement
10. Machine operational accuracy – PC evaluated
11. Run-out measurement of a spindle
12. Batch measurement of cylindrical parts
Task:
Measure the spacing R (distance between center points) of
clamping holes in the spring plate. Use the profile projector for
the measurement.
Measure and write down the coordinates of
tangents of measured holes!
Attention! – micrometrix thread has two revolutionsper milimeter Ring scale division is 50 scales.
Carefully read if you see the „half-milimeter line“
on the main scale + add the value from the ring.
Hole CoordinateCenter
coordinate
Diameter
value in axis
Diameter
valueSpacing
1
X1.1
X1.2
Y1.1
Y1.2
… … … …
Problem:
Decide about the applicability of the GO and NOT GO ends
(good and bad ends) of a workshop cylindrical plug gauge for
hole diameter control. Use the microindicator for measuring.
Deviation with a block gauge (40 mm) = -35
Deviation with a measured part = 12
Total deviation = 12-(-35) = 47
Scale = 0,001 mm
Dimension of deviation = 47 scales = 0,047 mm
Dimension of measured part = 40 + 0,047 = 40,047
mm
!!! Results discussion !!!
Problem:
Measure the frontal run out of a universal clamping head used for
workpieces clamping in both open and closed state.
Write down the values and express them by using a column chart.
(measured values in columns, separate columns for different places
of measurement).
Position [mm] clamp 1 2 3 4 Check no.1
Open -0,02 -0,01 0,01 -0,01 -0,02
Closed -0,04 -0,03 0,02 0,01 -0,04
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
clamp 1 2 3 4 open
closed
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
clamp 1 clamp 2 clamp3 clamp 4
open
closed
MAX
MIN
Runout = maximum value
ex. RUNOUT OF OPEN CLAMP = MAX-MIN
Problem:
Measure the radial and axial run-out of rotary (spindle) part
Express the results with a polar chart and mark the maximum run-
out value in this chart.
0.22
0.24
0.26
0.28
deviations for axial runout [mm]
Problem:
Measure the nominal thread diameter d2 and the
lead (pitch) of a metrical thread on given part.
Compare the measured values with nominal values in
table. Discuss the results.
Thread cross hair
movement of crosshaird2
3
2 1