linear and angular measurements

Sanjivani College Of Engineering, Kopargaon,Dist: Ahmednagar

Prof H.P.VaradeAssistant Professor

Engineering Metrology

Linear and Angular Measurements

UNIT- IMETROLOGY

AND MEASUREMENTS

05/03/23Mr.Harshal P.Varade,Asst.Professor,Sanjivani College of Engg,Kopargaon

2

MetrologyMetrology defines as the Science of pure measurement. But in engineering purposes, it in restricted to measurements of length and angles and other qualities which are expressed in linear or angular terms.

05/03/23 Mr.Harshal P.Varade,Asst.Professor,Sanjivani College of Engg,Kopargaon

3

Definition of Standards:

• A standard is defined as “something that is set up and established by an authority as rule of the measure of quantity, weight, extent, value or quality”.


4

Line and End standard measurements

• Line standardLength is expressed as the distance between two lines.• End standardLength is expressed as the distance between two flat

parallel faces


5

• Precision Degree of repetitiveness. If an instrument is not precise it will give different results for the same dimension for the repeated readings.

• Accuracy The maximum amount by which the result differ from true value(ie) Closeness to true value

Terminology in Measurment


6

• AccuracyAccuracy is how close a measured value is to the actual (true) value.

• PrecisionPrecision is how close the measured values are to each other.

Examples of Precision and Accuracy:


7

Types And Sources Of Errors

Systematic Errors• Systematic errors are regularly repetitive and can be

eliminated. • They results from improper condition or procedure of

experiment . • These error can be controlled & reduced if properly

analyze, so called as Controllable errors.Errors may be of four kinds; 1. Instrumental : For example, a poorly calibrated

instrument such as a thermometer that reads 102° C when immersed in boiling water and 2°C when immersed in ice water at atmospheric pressure. Such a thermometer would result in measured values that are consistently too high.


8

2. Observational : For example, parallax in reading a meter scale.

3. Environmental : Variation in atmospheric condition i.e. temperature, pressure etc. at place of measurement.

4. Stylus pressure :Variation in Force applied by anvils of micrometer on component to be measured results in different reading.

Random Errors• Random errors in experimental measurements are caused by unknown and

unpredictable changes in the experiment. These changes may occur in the measuring instruments or in the environmental conditions.

• Sources of random errors cannot always be identified. Possible sources of random errors are small variations in the position of setting standards and work piece, slight displacement of lever joints in the measuring joints in the measuring instrument.

• Examples of causes of random errors are:1. electronic noise in the circuit of an electrical instrument,2. Irregular changes in the heat loss rate from a solar collector due to changes

in the wind.• These error cannot be eliminated. 1. Observational : For example, errors in judgment of an observer when

reading the scale of a measuring device to the smallest division.2. Environmental : For example, unpredictable fluctuations in line voltage,

temperature, or mechanical vibrations of equipment.05/03/23 Mr.Harshal P.Varade,Asst.Professor,Sanjivani College of Engg,Kopargaon

10

Parallax Error :• Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.


11

Calibration

• Calibration is one of the primary processes used to maintain instrument accuracy.

• Calibration is the process of configuring an instrument to provide a result for a sample within an acceptable range.

• Measurement of Accuracy.• Establishment the relation of an instrument’s accuracy to the

international standard.

Success of Calibration

• Consistency of results obtained


12

Need of Calibration• Quality control & quality assurance in production.• To meet requirement of ISO• To comply with requirement of global market.• To promote international recognition.

Benefits of Calibration• Fulfils requirement of ISO 9000, ISO 14000. • As a proof that the instrument is working properly.• Confidence in using instrument.• Reduce rejection, failure rate.• Improved product & service quality leading to satisfied

customer.• Cost saving, safety.05/03/23 Mr.Harshal

P.Varade,Asst.Professor,Sanjivani College of Engg,Kopargaon

13

. Classification of measuring Instruments.

According to the functions:• Length measuring instrument•Angle measuring instrument•Instrument for checking deviation from geometrical forms•Instrument for determining the quality of surface finish.


14

Linear measuring instruments • Straight edge (Steel rule)• Outside caliper• Inside caliper• Vernier caliper• Outside micrometer• Inside micrometer• Vernier height gauge• Vernier depth gauge• Dial gauges


15

Angular measurements• Measuring the angle of Taper.

1. Bevel Protractor2. Tool Makers microscope3. Sine bar4. Auto Collimator5. Sine Centre


16

Slip Gauges •Gauge blocks (also known as gauge blocks, Johansson gauges, slip gauges) are a system for producing precision lengths. The individual gauge block is a metal or ceramic block that has been precision ground and lapped to a specific thickness.•For checking accuracy of venire calipers, micro metes, and such other measuring instruments.•Setting up a comparator to specific dimension.•For measuring angle of work piece and also for angular setting in conjunction with a sine bar.•The distances of plugs, spigots, etc. on fixture are often best measured with the slip gauges or end bars for large dimensions.•To check gap between parallel locations such as in gap gauges or between two mating parts.•Slip gauges are rectangular blocks of high grade steel with exceptionally close tolerances. These blocks are suitably hardened though out to ensure maximum resistance to wear. They are then stabilized by heating and cooling successively in stages so that hardening stresses are removed.


17

Measuring tools and instruments

Direct (contact) measurement(e.g. micrometer or caliper)

Indirect (non-contact) measurement(advanced methods such as optical,

ultrasonic, laser, etc.)

h Calipersh Gauges and Gauge Blocksh Sine Barh Special-purpose tools

h Rulesh Vernier Calipers h Vernier Gauges h Micrometersh Protractorsh Dial Indicators

Measuring tools and instruments

Graduated(either linear or angular graduations incorporated into measuring system of the tool)

Non-graduated(gauges or adjustable tools which compare the measurements)

Imperial steel rule with various lengthshaving graduations on each side

Same rule with relatively largergraduations

Metric steel rule with various lengthshaving graduations on each side

resolution?How to read a rule:h A = 12 mm (12th graduation)

h B = 22 mm (22nd graduation)

h C = 31.5 mm (between

h D = 40.5 mm (between

31st

40th

and 32nd)

and 41st)

Graduated Linear Measurement - Rules

Graduated Linear Measurement - Vernier Calipers

Direct reading of an internal lengthusing digital Vernier caliper Direct reading of an external length

using digital vernier caliper

Vernier caliper with a dial indicator

Graduated Linear Measurement - Vernier Calipers

Designed for use in toolrooms, workshops, inspection departments to measure or mark off verticalheights and locating center distances.

Standard Height gauge Dial Height Gauge Digital Height Gauge

Graduated Linear Measurement - Vernier Height Gauges

Designed for use in toolrooms, workshops, inspection departments to measure depths of holes, slots,recesses, and so on.

Standard Depth Gauge Dial Depth Gauge Digital Depth Gauge

Graduated Linear Measurement - Vernier Depth Gauges

THIMBLE READINGVERNIER READING

Metric Micrometer

SLEEVE (BARREL) READING

Metric Vernier Micrometer

Graduated Linear Measurement - Outside Micrometers

V-anvil Micrometer (measuring odd-fluted taps, millingcutters, reamers, and checking out of roundness)

Dial-indicating Micrometer

Screw Thread Micrometer(measuring pitch diameter

of screw threads)

Direct-readingMicrometer

Graduated Linear Measurement - Outside Micrometers

Standard Inside Micrometers Digital Inside Micrometers

Graduated Linear Measurement - Inside Micrometers

h Standard calipers have a fine adjustment screw and a quick-adjusting spring nut.

h Accuracy obtained with these tools depends mostly on the inherent skill of users.

h The measurements are carefully transferred to a graduated measuring tool.

Caliper for insidemeasurement

Caliper for outsidemeasurement

Caliper usedas a divider

Non-Graduated Linear Measurement - Calipers

Screw Pitch Gauges (consisting of a metal case containingmany separate leaves. Each leaf has teeth corresponding to

a definite pitch. By matching the teeth with the thread on work, the correct pitch can be read directly from the leaf)

Tap and Drill Gauges (consistingof a flat rectangular steel plate with

holes accurately drilled and identified according to their size) Radius Gauges (available as individual leaves and each

leaf is marked with its radius. They are designed to check both convex and concave radii)

Non-Graduated Linear Measurement - Special Purpose Gauges

Non-Graduated Linear Measurement - Rectangular Gauge Blocks

Slip Gauge Box

(a)

(b)SimpleProtractor (measuring angles from0 to 180º) Universal Bevel Protractor (main

scale consists of 4 portions of 90º)Measuring acute (a) and

obtuse (b) angles

How to read an angle on a bevel protractor:Main div. = 1º = 60´

Vernier div. = 1/12th of main div. ≈ 0.0833º = 5´

h The highest figure: 50 * (main div.) = 50ºh The matching figure: 4 * (vernier div.) ≈ 0.333º = 20´h The final reading is: ≈ 50.333º or 50º 20´

Graduated Angular Measurement - Protractors

*

Limitations of Sine Bar:

Maximum angle 45°

Sine Center – Maximum angle that can be measured is 60°

Non-Graduated Angular Measurement - Sine Bar

Comparators• Classification of comparators1. Mechanical2. Electrical and Electronics comparators3. Optical comparators4. Pneumatic comparators5. Fluid displacement comparators6. Projection comparators.7. Multi check comparators8. Automatic Gauging Machines9. Electro-Mech. Comparators.


32