The content of this book is a description of scientific, industrial and legal metrology. The technical subject fields of metrology and metrological. Engineering metrology is restricted to the measurement of length, angles To detect frauds in measurement or sale of goods and to book. produced and measured accurately for the machine tool to function as expected. ▷ Note: Metrology is a vast area. In this lecture, the main.
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It_Starts_With_Food__Discover_the_Whole30_-_Hartwig,bestthing.info It Starts With Food: Discover the Engineering Metrology and Measurements is a core subject for mechanical, Chapter 1 deals. Pdfdrive:hope Give books away. Engineering Metrology and Measurements is a core subject for mechanical, book provides a comprehensive coverage of both metrology and mechanical. The technical subject fields of metrology and metrological units are described IUPAP issues the “red book” on “Symbols, Units and Nomenclature in Physics”.
The sensor is not placed in contact with the object whose characteristics are being measured. The value of the quantity to be measured is in the beginning. The value of a quantity to be measured is replaced by a known value of the same quantity. If the position of the element indicating equilibrium is the same in both the cases.
The value of the quantity to be measured is complemented by a known value of the same quantity. Kilogram kg which is equal to the mass of International prototype of the kilogram. Data presentation element Basic units in SI system: Second s which is equal to the duration of periods of the radiation corresponding to the transition between the hyper fine levels of the ground state of the Caesium atom.
ME54 Generalized measuring system: The generalized measuring systems consist of the following common elements: Data transmission element 5. Definition by wavelength standard og sp ot. Variable manipulation element 4. Ampere A is that constant current which. Metre m which is equal to Primary sensing element 2.
Data processing element 6.
Laser interferometry for precision engineering metrology
Variable conversion element 3. Primary standard: It is only one material standard and is preserved under the most careful conditions and is used only for comparison with Secondary standard.
ME54 5 For Temperature: Secondary standard: It is similar to Primary standard as nearly as possible and is distributed to a number of places for safe custody and is used for occasional comparison with Tertiary standards.
Radian rad 2 For Solid angle: Steradian sr Derived SI units: Classification of Standards: In the Line standard. Mole mol is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.
If the instrument is required to measure a condition not varying with time characteristics are called static while for a time varying process variable measurement. Automatic and manually operated instruments 5.
Static response: The static characteristics of an instrument are considered for instruments which are used to measure an unvarying process conditions. Active and passive instruments. The instrument analysis of such dynamic response is called dynamic analysis of the measurement system. Analog and digital instruments m 1. Low grades of materials may be used.
Deflection and null type instruments. ME54 Tertiary standard: It is used for reference purposes in laboratories and workshops and is used for comparison with working standard. Intelligent instruments. Absolute and secondary instruments 7. Dynamic response: The behaviors of an instrument under such time varying input — output conditions called dynamic response of an instrument. Working standard: It is used daily in laboratories and workshops.
Measuring instruments: A broad classification of the instruments based on the application mode of operation. Contacting and non contacting instruments 6. Transient Terms in Measurement: Sensitivity of the instrument is defined as the ratio of the magnitude of the output signal to the magnitude of the input signal. It implies the ease with which observations can be made accurately.
It can also defined as the ability of the instruments to reproduce a group of the instruments as the same measured quantity under the same conditions.
It refers to repeatability or consistency of measurement when the instruments are carried out under identical conditions at a short interval of time. The readability is depends on the both the instruments and observer. It has wide range of the units which dependent up on the instrument or measuring system. It refers to how closely the measured value agrees with the true value.
ME54 Dynamic quantities are two types 1.
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The susceptibility of a measuring instrument to having its indications converted to a meaningful number. Correction is defined as a value which is added algebraically to the uncorrected result of the measurement to compensate to an assumed systematic error. Precision is defined as the degrees of exactness for which an instrument is designed or intended to perform. The errors may be constant or variable. The causes of these errors may be known or unknown.
Before we can read any instrument. For every kind of quantity to be measured. It is the measurement of measuring instrument. The value of the quantity reproduced by the physical measure and is indicated on that measure. Systematic errors are regularly repetitive in nature.
The operation of substituting the part for similar manufactured components of the shape and dimensions is known as interchangeability. It is the physical embodiment of a unit. The factor by which the indication of the instrument shall be multiplied to obtain the result of measurement. ME54 Calibration: Calibration is the process of determining and adjusting an instruments accuracy to make sure its accuracy is with in manufacturing specifications. It is the process of determining the values of the quantity being measured corresponding to a pre-established arbitrary scale.
The value of the quantity reproduced by the physical measure. Types of Errors: A Error of Measurement: It is the error which during several measurements. It is the error due to the friction between the moving parts of the measuring instruments.
Random errors are normally of limited time duration. Random errors are non-consistent. It is the error. It is the reading error which is produced. It is the difference between the value indicated by the measuring mechanism and the conventional true value of the measured quantity. It is the difference between the nominal value and the conventional true value reproduced by the physical measure.
It is the error due to the inertia mechanical. It is the error of a measuring instrument arising from the fact that the values of the influence quantities are different from those corresponding to the reference conditions. It is the indication of a measuring instrument for the zero value of the quantity measured.
It is the difference between the measured values of a quantity. It is the difference between the conventional true value reproduced by the physical measure and the nominal value of that measure. It is the error arising from the fact that the temperature of instrument does not maintain its reference value. C Error of observation: It is the error of observation resulting from incorrect reading of the indication of a measuring instrument by the observer.
ME54 identical conditions. The two common practices to minimise this error are: As the name implies. If there is any variation in the ambient condition.
Chaotic errors are random errors but unlike the latter. Though the pressure involved during measurement is generally small. These are random errors which are not controllable. This will cause an error in the measurement. D Based on nature of errors: Avoidable errors: These errors may occur due to parallax in the reading of measuring instruments.
ME54 3 Interpolation error: It is the reading error resulting from the inexact evaluation of the position of the index with regard to two adjacent graduation marks between which the index is located. This occurs when the scale and pointer are separated relative to one another. These avoidable errors occur also due to non-alignment of work piece centers. This will cause an error of constant magnitude.
Of the three. These can be calibration errors. These are caused due to variation in the calibrated scale from its normal value. The actual length of standards such as slip gauges will vary from the nominal value by a small amount.
The sources of error are known and it is possible to have a control on these sources. Instruments are calibrated at these conditions. These include mistakes and blunders.
Uses of Comparator: Angular measurements: Sine bar.
Slip gauges and classification. It does not measure the actual dimension but indicates how much it differs from the basic dimension working standard.
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Optical bevel protractor Comparator: It is a precision instrument employed to compare the dimension of a given component with a working standard generally slip gauges.
Definition of metrology-Linear measuring instruments: Roller gauges: Cylindrical rollers with their lengths equal to their diameters may be used as gauges.
Select the next smallest figure in the same way. These gauges are other wise called as Gauge blocks or Block gauges and are universally accepted as end standards of length in industry.
These blocks are highly hardened more than HV through out to ensure maximum resistance to wear and are then stabilised by heating and cooling successively in stages so that the hardening stresses are removed.
Slip gauges are rectangular blocks of high grade steel or tungsten carbide with less co-efficient of thermal expansion.
Engineering Metrology and Measurements.pdf
Selection of Slip gauges for required dimension: Always start with the last decimal place and deduct this from the required dimension.
ME54 4 Electrical comparator 5 Fluid displacement comparator 6 Pneumatic comparator a Back pressure comparator b Flow — velocity Pneumatic comparator In addition. The air gap between the gauge faces is expelled out and the adhesion is caused partly by molecular attraction and partly by atmospheric pressure.
The cross sections of these gauges are 9 x 30 mm for sizes up to 10 mm and 9 x 35 mm for larger sizes. The gap between the two wrung slip gauges is only of the order of 0.
Limit gauges: These are inspection tools for rigid design. After hardening. Minimum number of slip gauges should be selected to build up the given dimension.
These are produced to fine tolerances. The dimension height is marked on one of the measuring faces of gauge blocks. The bush is check by a plug gauge which in so far as the form of its surface and its size is concerned.
This is applied to upper limit of a shaft and lower limit of a hole. They can only be used for determining as to whether the inspection parts are made within the specified limits.
Gauge Design: Every gauge is a copy of the part which mates with the part for which the gauge is designed. These gauges are made up of suitable wear resisting steel and are normally hardened to not less than HV and suitably stabilized and ground and lapped. Generally a small circumferential groove is cut near the leading end of the gauge and the remaining short cylindrical surface is slightly reduced in order to act as a pilot.
The gauging surface is in the form of an external cylinder. The gauging surface is in the form of a sphere from which two equal segments are cut off by planes normal to the axis of the handle. ME54 work. According to Taylor. For example. The gauging surface is in one of the two forms: It is similar to full form spherical plug gauge but has two equal segments cut off by planes parallel to the axis of the handle in addition to the segments cut off by planes normal to the axis of the handle.
This is applied to lower limit of a shaft and the upper limit of a hole. It has one flat surface and one cylindrical surface. ME54 5 Segmental cylindrical bar gauge with reduced measuring faces: It is similar to the segmental cylindrical bar gauge but has reduced measuring faces in a plane parallel to the axis of the handle.
For testing the external taper of the tanged end shank.. If the ray passing through the geometric centre of the lens is considered. The various types of limit gauges used for gauging external diameters of shaft are: The gauging surface is in the form of an internal cylinder and whose wall is thick enough to avoid deformation under normal conditions of use.
It has spherical end surfaces which form part of one single sphere. B and C. The gauges for internal taper are marked with a ring on the gauge planes another ring to indicate the minimum depth of internal taper. At the extreme position. If this parallel beam now strikes a plane reflector which is normal to the optical axis.
The surfaces constituting the working size may both be flat or both cylindrical also. It is essentially an infinity telescope and a collimator combined into one instrument. The important points about this collimation of a beam of light are: The shank surfaces may however.
The error in the work angle is the difference in the two readings on the illuminated scale. It is a precision measuring instrument and is an excellent example of combination of linear measurement and angular measurement when used in conjunction with gauge blocks slip gauges. The work is now slowly rotated until the illuminated scale moves across the fixed scale.
The image falls. It is made of high carbon.
It is now replaced by the work. It is reflected. ME54 c Although the distance of the reflector does not affect the reading x. The setup consists of a lapped flat and reflective base above which the optical details are mounted in a tube on an adjustable bracket. This feature enables angular errors in two planes to be dealt with or more important.
It is then projected as a parallel beam and strikes a plane reflector below the instrument. The gauge block can usefully be held in place with elastic bands. It should be used on a grade A surface plate.
For getting better readability the instrument scale should be as high as possible. Accuracy: cl u si Readability is defined as the closeness with which the scale of an analog instrument can be read. The susceptibility of a measuring instrument to having its indications converted to a meaningful number.
It implies the ease with which observations can be made accurately. The readability is depends on the both the instruments and observer. It is the process of determining the values of the quantity being measured corresponding to a pre-established arbitrary scale. It is the measurement of measuring instrument. The quantity to be measured is the input to the measuring instrument.
The amount of output is governed by that of input. Before we can read any instrument, a scale must be framed for the output by successive application of some already standardized inputs signals. This process is known as calibration. Types of Errors: A Error of Measurement: 1 Systematic error: It is the error which during several measurements, made under the same conditions, of the same value of a certain quantity, remains constant in absolute value and sign or varies in a predictable way in accordance with a specified law when the conditions change.
The causes of these errors may be known or unknown. The errors may be constant or variable. Systematic errors are regularly repetitive in nature. The operation of substituting the part for similar manufactured components of the shape and dimensions is known as interchangeability. Random errors are non-consistent. Random errors are normally of limited time duration.
It is the error, often gross, which results from incorrect execution of B Instrumental error: 1 Error of a physical measure: It is the difference between the nominal value and the conventional true value reproduced by the physical measure.Tactile sensors: Cylindrical rollers with their lengths equal to their diameters may be used as gauges. Uses of Comparator: ME54 D. List of Books. You have entered an incorrect email address!
This will cause an error of constant magnitude. June Primary standard: Measurement of screw threads.