CHAP(35) 35 Engr Metrology & Instrumentation.pdf

Engineering Metrology and Instrumentation

Chapter 35 Engineering Metrology and Instrumentation

Engineering Metrology and Instrumentation 

Engineering metrology-measurement of dimensions: length, thickness, diameter, taper angle, flatness, profiles, and others.  Post-process inspection  In-process inspection  Dimensional tolerance

Engineering Metrology and Instrumentation 

Measurement and Instruments used

Engineering Metrology and Instrumentation 

Measurement Standards Linear measure-inch, foot, yard, meter Standards kept by governments; meter=1,650763.73 wavelengths Kr.  Sensitivity-also called resolution, is the smallest  

difference in dimensions that the instrument can detect or distinguish.  Precision-the degree to which the instrument gives repeated measurements of the same standard.

Engineering Metrology and Instrumentation 

Line graduated Instruments 

Linear measurements(direct reading) Rules Vernier calipers  Micrometers  Diffraction gratings  

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Engineering Metrology and Instrumentation

Engineering Metrology and Instrumentation

Reading a Micrometer Tenths

0._

Hundredths

0.0_

Thousandths

0.00_

Tenthousandths

0.000_

Total

0.____

0.3 0.075 0.007 0.382

Engineering Metrology and Instrumentation 

Linear Measurements(indirect reading)

0.4 0.000 0.005 0.405

Engineering Metrology and Instrumentation 

Calipers  Dividers

Comparative measuring instruments Dial indicators Electronic gages  Laser scan micrometers

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0.2 0.050 0.020+ 0.270+

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Angle measuring instruments Bevel protractor Sine bar  Surface plate  Angle gage blocks  

Engineering Metrology and Instrumentation 

Geometric features 

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autocollimator

Flatness  

Interferometry/optical flat Laser interferometry

Roundness 

Straightness 

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Engineering Metrology and Instrumentation Total indicator reading

Profile  Screw threads & Gear teeth  Optical contour projectors 

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Engineering Metrology and Instrumentation 

More pictures

Engineering Metrology and Instrumentation 

Engineering Metrology and Instrumentation

Gages

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Engineering Metrology and Instrumentation 

Gage blocks  Fixed gages  Pneumatic gages

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Automated measurement  

Sensor systems Laser measurement

Optical instruments Microscopes Bore scopes  Light section microscope  Scanning electron microscope

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Engineering Metrology and Instrumentation

Coordinate measuring and layout machines

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Engineering Metrology and Instrumentation 

General characteristics and selection Accuracy

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Amplification

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Calibration

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Drift

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Linearity

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Repeat accuracy Resolution Rule of 10 Sensitivity stability

Magnification

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Engineering Metrology and Instrumentation 

Geometric Dimensioning and Tolerancing

Engineering Metrology and Instrumentation 

Tolerance concerns

Dimensional tolerancing  Importance of tolerance control 

Engineering Metrology and Instrumentation 

GD&T Symbols

Engineering Metrology and Instrumentation           

Allowance Basic size Bilateral tolerance Clearance Clearance fit Datum Feature Fit Geometric tolerancing Hole-basis system interferance

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Interferance fit IT Grade Limit dimensions Macumum material condition Nominal size Positional tolerancing Shaft-basis system Standard size Transition fit Unilateral tolerancing Zero line

Engineering Metrology and Instrumentation 

Limits and fits      

Running and sliding Locational clearance Locational transition Locational interferance Force and shrink Metric classification

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