Linear and angular measurements
- 1. Sanjivani College Of Engineering, Kopargaon, Dist: Ahmednagar Prof H.P.Varade Assistant Professor Engineering Metrology Linear and Angular Measurements
- 3. Metrology Metrology 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. 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 3
- 4. 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”. 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 4
- 5. Line and End standard measurements • Line standard Length is expressed as the distance between two lines. • End standard Length is expressed as the distance between two flat parallel faces 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 5
- 6. • 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 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 6
- 7. • Accuracy Accuracy is how close a measured value is to the actual (true) value. • Precision Precision is how close the measured values are to each other. Examples of Precision and Accuracy: 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 7
- 8. 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. 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 8
- 9. 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.
- 10. 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.06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 10
- 11. 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. 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 11
- 12. 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 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 12
- 13. 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.06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 13
- 14. . 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. 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 14
- 15. 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 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 15
- 16. Angular measurements • Measuring the angle of Taper. 1. Bevel Protractor 2. Tool Makers microscope 3. Sine bar 4. Auto Collimator 5. Sine Centre 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 16
- 17. 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.06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani 17
- 18. 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 Calipers h Gauges and Gauge Blocks h Sine Bar h Special-purpose tools h Rules h Vernier Calipers h Vernier Gauges h Micrometers h Protractors h 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)
- 19. Imperial steel rule with various lengths having graduations on each side Same rule with relatively larger graduations Metric steel rule with various lengths having 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
- 20. Graduated Linear Measurement - Vernier Calipers
- 21. Direct reading of an internal length using digital Vernier caliper Direct reading of an external length using digital vernier caliper Vernier caliper with a dial indicator Graduated Linear Measurement - Vernier Calipers
- 22. Designed for use in toolrooms, workshops, inspection departments to measure or mark off vertical heights and locating center distances. Standard Height gauge Dial Height Gauge Digital Height Gauge Graduated Linear Measurement - Vernier Height Gauges
- 23. 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
- 24. THIMBLE READINGVERNIER READING Metric Micrometer SLEEVE (BARREL) READING Metric Vernier Micrometer Graduated Linear Measurement - Outside Micrometers
- 25. V-anvil Micrometer (measuring odd-fluted taps, milling cutters, reamers, and checking out of roundness) Dial-indicating Micrometer Screw Thread Micrometer (measuring pitch diameter of screw threads) Direct-reading Micrometer Graduated Linear Measurement - Outside Micrometers
- 26. Standard Inside Micrometers Digital Inside Micrometers Graduated Linear Measurement - Inside Micrometers
- 27. 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 inside measurement Caliper for outside measurement Caliper used as a divider Non-Graduated Linear Measurement - Calipers
- 28. Screw Pitch Gauges (consisting of a metal case containing many 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 (consisting of 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
- 29. Non-Graduated Linear Measurement - Rectangular Gauge Blocks Slip Gauge Box
- 30. (a) (b)Simple Protractor (measuring angles from 0 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.) = 50º h The matching figure: 4 * (vernier div.) ≈ 0.333º = 20´ h The final reading is: ≈ 50.333º or 50º 20´ Graduated Angular Measurement - Protractors
- 31. * Limitations of Sine Bar: Maximum angle 45° Sine Center – Maximum angle that can be measured is 60° Non-Graduated Angular Measurement - Sine Bar
- 32. Comparators • Classification of comparators 1.Mechanical 2.Electrical and Electronics comparators 3.Optical comparators 4.Pneumatic comparators 5.Fluid displacement comparators 6.Projection comparators. 7.Multi check comparators 8.Automatic Gauging Machines 9.Electro-Mech. Comparators. 06/06/16 Mr.Harshal P.Varade,Asst.Professor,Sanjivani College of Engg,Kopargaon 32