Practical metrology spo. Workshop on metrology, standardization and certification
transcript
1 MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION Federal State Autonomous educational institution higher education "NATIONAL RESEARCH TOMSK POLYTECHNICAL UNIVERSITY" A.S. Spiridonova, N.M. Natalinova WORKSHOP ON METROLOGY, STANDARDIZATION AND CERTIFICATION Recommended as a teaching aid by the Editorial and Publishing Council of Tomsk Polytechnic University Publishing house of Tomsk Polytechnic University 2014
2 UDC (076.5) LBC ya73 С72 С72 Spiridonova A.S. Workshop on metrology, standardization and certification: textbook / A.S. Spiridonova, N.M. Natalinova; Tomsk Polytechnic University. Tomsk: Publishing House of the Tomsk Polytechnic University, p. The manual contains six laboratory works and four practical exercises, which include the necessary theoretical materials and test questions to prepare for the defense of the work performed. It is intended for students of all directions to consolidate the theoretical foundations of metrology, measurement methods, the procedure for measuring the values of physical quantities and the rules for processing measurement results, estimating the uncertainty of measurements, the legal foundations of metrology, as well as the theoretical provisions of standardization activities, the principles of construction and rules for using standards, complexes standards and other regulatory documents. UDC (076.5) LBC Ya73 Reviewers Candidate of Technical Sciences, Associate Professor of TSUAE A.A. Alekseev Candidate of Chemical Sciences, Associate Professor of TSU N.A. Gavrilenko FGAOU VO NR TPU, 2014 Spiridonova A.S., Natalinova N.M., 2014 Design. Publishing house of Tomsk Polytechnic University, 2014
3 INTRODUCTION Metrology and standardization are tools for ensuring the quality and safety of products, works and services, an important aspect of a multifaceted activity. Quality and safety are the main factors in the sale of goods. The purpose of teaching the discipline "Metrology, standardization and certification" is the presentation of concepts, the formation of students' knowledge, skills and abilities in the areas of standardization, metrology and conformity assessment to ensure the efficiency of production and other activities. As a result of studying the discipline, the student must have the following competencies: to know the goals, principles, areas of application, objects, subjects, means, methods, the regulatory framework for standardization, metrology, conformity assessment activities; be able to apply technical and metrological legislation; work with normative documents; recognize conformity confirmation forms; distinguish between international and national units of measurement; have experience in working with current federal laws, regulatory and technical documents necessary for the implementation of professional activities. The work complies with the requirements of the State Educational Standard of Higher Professional Education (FSES HPE and TPU OOP standards) in the discipline "Metrology, standardization and certification" for students of all specialties. This manual is intended to consolidate the theoretical foundations of metrology, measurement methods, the procedure for measuring the values of physical quantities and the rules for processing measurement results, the legal framework of metrology, as well as the theoretical provisions of standardization and certification activities, the principles of construction and rules for using standards, sets of standards and other regulatory documentation. 3
4 SECTION 1. METROLOGY LABORATORY WORK 1 CLASSIFICATION OF MEASURING INSTRUMENTS AND RATED METROLOGICAL CHARACTERISTICS 1.1. Basic concepts and definitions In accordance with the RMG, a measuring instrument is a technical instrument intended for measurements, having normalized metrological characteristics, reproducing and (or) storing a unit of physical quantity, the size of which is taken unchanged (within a specified error) for a known time interval. Measuring instruments (SI) used in various fields of science and technology are extremely diverse. However, for this set, it is possible to single out some common features inherent in all SI, regardless of the field of application. These features form the basis of various SI classifications, some of which are given below. Classification of measuring instruments By technical purpose: A measure of a physical quantity is a measuring instrument designed to reproduce and (or) store a physical quantity of one or more given dimensions, the values of which are expressed in established units and are known with the required accuracy; The following types of measures are distinguished: a single-valued measure is a measure that reproduces a physical quantity of the same size (for example, a 1 kg weight, a capacitor of constant capacitance); multi-valued measure - a measure that reproduces a physical quantity of different sizes (for example, a dashed measure of length, a capacitor of variable capacitance); set of measures set of measures different size the same physical quantity, intended for practical use both individually and in various combinations (for example, a set of gage blocks); store measures set of measures structurally combined into single device, in which there are devices for connecting them in various combinations (for example, a store electrical resistance). 4
5 Measuring device is a measuring instrument designed to obtain the values of the measured physical quantity in the specified range. The measuring device, as a rule, contains a device for converting the measured value into a signal of measuring information and indexing it in the most accessible form for perception. In many cases, the display device has a scale with an arrow or other device, a chart with a pen or a digital display, thanks to which a reading or registration of the values of a physical quantity can be made. Depending on the type of output value, analog and digital measuring instruments are distinguished. An analog measuring instrument is a measuring instrument whose readings (or output signal) are a continuous function of the measured quantity (eg pointer voltmeter, mercury-in-glass thermometer). A digital meter is a meter whose readings are presented in digital form. In a digital device, the input analog signal of the measuring information is converted into a digital code, and the measurement result is displayed on a digital display. According to the form of presentation of the output value (according to the method of indicating the values of the measured value), measuring instruments are divided into indicating and recording measuring instruments. indicating measuring instrument a measuring instrument that only allows reading the values of the measured quantity (micrometer, analog or digital voltmeter). recording measuring device measuring device in which the recording of readings is provided. The registration of the values of the measured value can be carried out in analog or digital form, in the form of a diagram, by printing on paper or magnetic tape (thermograph or, for example, a measuring device associated with a computer, display and device for printing readings). By action, measuring instruments are divided into integrating and summing. There are also direct action devices and comparison devices. A measuring transducer is a technical tool with standard metrological characteristics that serves to convert a measured value into another value or a measuring signal that is convenient for processing, storage, further transformations, indication or transmission. The resulting value 5
6 or the measuring signal are not directly accessible to the observer, they are determined through the conversion factor. A measuring transducer is either part of a measuring device (measuring setup, measuring system), or is used together with any measuring instrument. According to the nature of the conversion, analog, digital-to-analog, analog-to-digital converters are distinguished. According to the place in the measuring circuit, primary and intermediate converters are distinguished. There are also scale and transmitting converters. Examples: thermocouple in a thermoelectric thermometer, measuring current transformer, electro-pneumatic converter. Measuring installation is a set of functionally combined measures, measuring instruments, measuring transducers and other devices, designed to measure one or more physical quantities and located in one place. The measuring setup used for verification is called a calibration setup. The measuring setup that is part of the standard is called the reference setup. Some large measuring installations are called measuring machines, designed to accurately measure the physical quantities that characterize the product. Examples: installation for measuring the resistivity of electrical materials, installation for testing magnetic materials. Measuring system is a set of functionally combined measures, measuring instruments, measuring transducers, computers and other technical means located at different points of a controlled object, etc., with the aim of measuring one or more physical quantities inherent in this object, and generating measuring signals for different purposes . Depending on the purpose, measuring systems are divided into measuring information, measuring control, measuring control systems, etc. A measuring system that is reconfigured depending on a change in the measuring task is called a flexible measuring system (GIS). Examples: measuring system of a thermal power plant, which allows obtaining measuring information about a number of physical quantities in different power units. It can contain hundreds of measurement channels; a radio navigation system for determining the location of various objects, consisting of a number of measuring and computing complexes spaced apart in space at a considerable distance from each other. 6
7 Measuring and computing complex is a functionally integrated set of measuring instruments, computers and auxiliary devices designed to perform a specific measuring task as part of a measuring system. Comparator means of comparison intended for comparison of measures of homogeneous quantities (lever balance, comparator for comparison of normal elements). According to the metrological purpose, all SI are divided into standards, working standards and working SI. The standard of a physical quantity unit (standard) is a measuring instrument (or a set of measuring instruments) intended for reproduction and (or) storage of a unit and transfer of its size to measuring instruments lower in the verification scheme and approved as a standard in the prescribed manner. The design of the standard, its properties and the method of reproducing the unit are determined by the nature of the given physical quantity and the level of development of measuring technology in this area of measurement. The standard must have at least three essential features of immutability, reproducibility and comparability that are closely related to each other. Working standard A standard designed to transfer the size of a unit to working measuring instruments. If necessary, working standards are divided into categories (1st, 2nd, ..., nth). In this case, the transfer of the size of the unit is carried out through a chain of working standards subordinate in terms of digits. At the same time, from the last working standard in this chain, the size of the unit is transferred to the working measuring instrument. A working measuring instrument is a measuring instrument intended for measurements not related to the transfer of the size of a unit to other measuring instruments. According to the significance of the measured physical quantity, all measuring instruments are divided into main and auxiliary measuring instruments. The main means of measuring SI of that physical quantity, the value of which must be obtained in accordance with the measurement task. Auxiliary measuring instruments SI of that physical quantity, the influence of which on the main measuring instrument or object of measurement must be taken into account in order to obtain measurement results of the required accuracy (a thermometer for measuring gas temperature in the process of measuring the volume flow of this gas). 7
8 The classification of measuring instruments according to their technical purpose is the main one and is shown in Fig. 1.1 Metrological characteristic of a measuring instrument (MX SI): Characteristic of one of the properties of a measuring instrument that affects the measurement result and its error. For each type of measuring instruments, their metrological characteristics are established. The metrological characteristics established by normative and technical documents are called standardized metrological characteristics, and those determined experimentally are called valid metrological characteristics. The nomenclature of metrological characteristics and methods for their normalization are established by GOST. All metrological characteristics of MI can be divided into two groups: characteristics that affect the result of measurements (determining the scope of MI); characteristics affecting the accuracy (quality) of the measurement. The main metrological characteristics that affect the result of measurements include: measurement range of measuring instruments; eight
9 the value of a one-to-one or multi-valued measure; transmitter conversion function; the value of division of the scale of a measuring instrument or a multi-valued measure; type of output code, number of digits of the code, price of the unit of the smallest digit of the code of measuring instruments intended for issuing results in a digital code. Measuring range of a measuring instrument (measurement range) is the range of values within which the permissible error limits of a measuring instrument are normalized (for transducers, this is the conversion range). The values of the quantity that limit the measurement range from below and above (left and right) are called the lower measurement limit or the upper measurement limit, respectively. For measures, the limits of reproduction of values. Single digit measures have nominal and actual reproducible values. The nominal value of a measure is the quantity value assigned to a measure or batch of measures during manufacture. Example: resistors with a nominal value of 1 ohm, a weight with a nominal value of 1 kg. Often the nominal value is indicated on the measure. The actual value of a measure is the value of a quantity assigned to a measure based on its calibration or verification. Example: the composition of the state standard of the unit of mass includes a platinum-iridium weight with a nominal mass value of 1 kg, while the actual value of its mass is 1 kg, obtained as a result of comparisons with the international standard of the kilogram stored at the International Bureau of Weights and Measures (BIPM) (in in this case it is the calibration). The range of indications of a measuring instrument (range of indications) is the range of values of the instrument scale, limited by the initial and final values of the scale. Measuring range of a measuring instrument (range of measurements) is the range of values within which the permissible error limits of a measuring instrument are normalized. The values of the quantity that limit the measurement range from below and above (left and right) are called the lower measurement limit or the upper measurement limit, respectively. The scale division price (division price) is the difference between the values of the quantities corresponding to two adjacent marks on the scale of the measuring instrument. The metrological characteristics that determine the accuracy of measurement include the error of the measuring instrument and the accuracy class of the measuring instrument. 9
10 Measuring instrument error is the difference between the indication of the measuring instrument (x) and the true (real) value (x d) of the measured physical quantity. x x x d. (1.1) As x d is either a nominal value (for example, measures), or the value of a quantity measured more accurate (at least an order of magnitude, i.e., 10 times) SI. The smaller the error, the more accurate the measuring instrument. MI errors can be classified according to a number of features, in particular: in relation to the measurement conditions, basic, additional; according to the method of expression (by the method of normalization of MX) absolute, relative, reduced. The basic error of a measuring instrument (basic error) is the error of a measuring instrument used under normal conditions. As a rule, normal operating conditions are: temperature (293 5) K or (20 5) ºС; relative air humidity (65 15)% at 20 ºС; mains voltage 220 V 10% with a frequency of 50 Hz 1%; atmospheric pressure from 97.4 to 104 kPa. Additional error of a measuring instrument (additional error) is a component of the error of a measuring instrument that occurs in addition to the main error due to the deviation of any of the influencing quantities from its normal value or due to its going beyond the normal range of values. When normalizing the characteristics of the errors of measuring instruments, the limits of permissible errors (positive and negative) are established. The limits of permissible basic and additional errors are expressed in the form of absolute, reduced or relative errors, depending on the nature of the change in errors within the measurement range. The limits of the permissible additional error can be expressed in a form different from the form of expression of the limits of the permissible basic error. The absolute error of the measuring instrument (absolute error, expressed in unity of error) is the error of the measuring instrument in the values of the measured physical quantity. The absolute error is determined by formula (1.1). ten
11 The limits of the permissible basic absolute error can be specified as: a (1.2) or a bx, (1.3) where the limits of the permissible absolute error, expressed in units of the measured value at the input (output) or conventionally in scale divisions; x the value of the measured value at the input (output) of measuring instruments or the number of divisions counted on the scale; ab, positive numbers independent of x. The reduced error of the measuring instrument (reduced error) is the relative error expressed as the ratio of the absolute error of the measuring instrument to the conditionally accepted value of the quantity (normalizing value), which is constant over the entire measurement range or in part of the range. The reduced error of the measuring instrument is determined by the formula: 100%, (1.4) x N where the limits of the allowable reduced basic error, %; limits of permissible absolute basic error, established by formula (1.2); x N normalizing value expressed in the same units as. The limits of the allowable reduced basic error should be set in the form: p, (1.5) where p is an abstract positive number chosen from the series 1 10 n ; 1.5 10n; (1.6 10n); 2 10n; 2.5 10n; (3 10 n); 4 10n; 5 10n; 6 10 n (n = 1, 0, 1, 2, etc.). The normalizing value x N is taken equal to: the final value of the working part of the scale (x k), if the zero mark is on the edge or outside the working part of the scale (uniform or exponential); the sum of the final values of the scale (excluding the sign), if the zero mark is inside the scale; the modulus of the difference in measurement limits for SI, the scale of which has a conditional zero; the length of the scale or its part corresponding to the measurement range, if it is significantly non-uniform. In this case, the absolute error, like the length of the scale, must be expressed in millimeters. eleven
12 Relative error of the measuring instrument (relative error) error of the measuring instrument, expressed as the ratio of the absolute error of the measuring instrument to the measurement result or to the actual value of the measured physical quantity. The relative error of the measuring instrument is calculated by the formula: 100%, (1.6) x where the limits of the permissible relative basic error, %; limits of permissible absolute error, expressed in units of the measured value at the input (output) or conventionally in scale divisions; x value of the measured quantity at the input (output) of measuring instruments or the number of divisions counted on the scale. If bx, then the limits of the permissible relative basic error are set in the form: q, (1.7) where q is an abstract positive number selected from the series given a bx, then in the form: given above; or if x cd k 1, (1.8) x where x k is greater (in absolute value) from the measurement limits; cd, positive numbers chosen from the series above. In justified cases, the limits of the permissible relative basic error are determined by more complex formulas or in the form of a graph or table. The characteristics introduced by GOST 8.009 most fully describe the metrological properties of SI. However, there are currently quite a few a large number of SI, the metrological characteristics of which are normalized in a slightly different way, namely on the basis of accuracy classes. Accuracy class of measuring instruments (accuracy class) generalized characteristic of this type measuring instruments, as a rule, reflecting the level of their accuracy, expressed by the limits of permissible basic and additional errors, as well as other characteristics that affect accuracy. The accuracy class makes it possible to judge the limits of the measurement error of this class. This is important when choosing measuring instruments depending on the given measurement accuracy. 12
13 The designation of accuracy classes of SI is assigned in accordance with GOST. The construction rules and examples of the designation of accuracy classes in the documentation and on measuring instruments are given in Appendix B. The designation of the accuracy class is applied to dials, shields and SI cases, and is given in the regulatory documentation for SI. The range of standardized metrological characteristics of measuring instruments is determined by the purpose, operating conditions, and many other factors. The norms for the main metrological characteristics are given in the standards, in the technical specifications (TS) and operational documentation for SI The purpose of the work is to familiarize yourself with the technical documentation for SI and determine the main classification features and normalized metrological characteristics of the measuring instruments used; acquisition of skills in determining the main classification features, the measuring instruments used and their standardized metrological characteristics directly on the measuring instruments; consolidation of theoretical knowledge in the section "Classification of measuring instruments" of the studied discipline "Metrology, standardization and certification" Used equipment and instruments 1) oscilloscope; 2) digital voltmeter; 3) analog voltmeter; 4) generator; 5) amplifier; 6) power supply; 7) the element is normal temperature-controlled; 8) programmable source of calibrated voltages Work program Determine the classification features indicated in Table. 1.2 from among the measuring instruments (MI) at the workplace Familiarize yourself with the technical documentation for the MI (operating manual, technical description with instruction manual or passport). 13
14 Determine the normalized metrological characteristics of MI directly by measuring instruments and technical documentation for them and fill in the table for each measuring instrument Compile a report on the work done (see Appendix A for an example of a title page). Table 1.2 Classification features Measuring instrument (indicate the type of MI) By type (by technical purpose) By type of output value By the form of information presentation (only for measuring instruments) By purpose By metrological purpose Normalized metrological characteristics 1.5. Control questions 1. Name the types of measuring instruments. 2. According to what classification criteria are SI subdivided. 3. Describe each type of MI. 4. What groups are the metrological characteristics of SI divided into. 5. What are metrological characteristics? 6. What are normalized and valid metrological characteristics and how do they differ from metrological characteristics? 7. Name the metrological characteristics that determine: the scope of the SI; measurement quality. 8. Name the types of errors. 9. What characteristic determines the accuracy of SI? 10. What is the function of standards? 11. What is the difference in the appointment of working SI and working standards? 1.6. Literature 1. RMG GSI. Metrology. Basic terms and definitions. Recommendations for interstate standardization. 2. GOST GSI. Normalized metrological characteristics of measuring instruments. 3. GOST GSI. Accuracy classes of measuring instruments. 4. Sergeev A.G., Teregerya V.V. Metrology, standardization and certification. M.: Yurayt Publishing House: ID Yurayt,
15 LABORATORY WORK 2 INDIRECT SINGLE MEASUREMENTS 2.1. Basic concepts and definitions Measurement is a set of operations for the use of a technical means that stores a unit of a physical quantity, providing a ratio (in an explicit or implicit form) of the measured quantity with its unit and obtaining the value of this quantity. Measurements are the main source of information about the compliance of products with the requirements of regulatory documents. Only the reliability and accuracy of measurement information ensure the correctness of decision-making about the quality of products, at all levels of production when testing products, in scientific experiments, etc. Measurements are classified: a) by the number of observations: a single measurement a measurement performed once. The disadvantage of these measurements is the possibility of a gross miss error; multiple measurement measurement of a physical quantity of the same size, the result of which is obtained from several successive measurements, i.e., consisting of a number of single measurements. Usually their number is n 3. Multiple measurements are carried out in order to reduce the influence of random factors on the measurement result; b) by the nature of accuracy (according to the conditions of measurement): equal-precision measurements of a series of measurements of any quantity, made with the same accuracy of measuring instruments in the same conditions with the same care; unequal measurements - a series of measurements of some quantity, performed by several measuring instruments that differ in accuracy and (or) under different conditions; c) by expression of the measurement result: absolute measurement is a measurement based on direct measurements of one or more fundamental quantities and (or) the use of physical constant values (for example, the measurement of force F m g is based on the measurement of the basic quantity of mass m and the use of the physical constant of gravitational acceleration g (at the point of measurement of mass); relative measurement is the measurement of the ratio of a quantity to the quantity of the same name, which plays the role of a unit, or the measurement of a change
16 values in relation to the value of the same name, taken as the original; d) according to the method of obtaining the measurement result: direct measurement is a measurement in which the desired value of a physical quantity is obtained directly (for example, measuring the mass on a scale, measuring the length of a part with a micrometer); indirect measurement is the determination of the desired value of a physical quantity based on the results of direct measurements of other physical quantities that are functionally related to the sought value; cumulative measurements are simultaneous measurements of several quantities of the same name, in which the desired values \u200b\u200bof the quantities are determined by solving a system of equations obtained by measuring these quantities in various combinations (for example, the mass value of individual weights of the set is determined from the known value of the mass of one of the weights and from the measurement results ( comparisons) masses of various combinations of weights); joint measurements are simultaneous measurements of two or more dissimilar quantities to determine the relationship between them; e) by the nature of the change in the measured physical quantity: static measurement is the measurement of a physical quantity taken in accordance with a specific measurement task as unchanged throughout the measurement time. They are carried out with the practical constancy of the measured quantity; dynamic measurement measurement of a physical quantity that changes in size; f) according to the metrological purpose of the measuring instruments used: technical measurements measurements using working measuring instruments; metrological measurements measurements with the help of reference measuring instruments in order to reproduce units of physical quantities in order to transfer their size to working measuring instruments. The measurement results are approximate estimates of the values of quantities found by measurements, since even the most accurate instruments cannot show the actual value of the measured quantity. There is necessarily a measurement error, the causes of which can be various factors. They depend on the method of measurement, on the technical means by which measurements are taken, and on the perception of the observer making the measurements. 16
17 The accuracy of the measurement result is one of the characteristics of the quality of measurement, reflecting the closeness to zero of the error of the measurement result. The smaller the measurement error, the greater its accuracy. Measurement error x deviation of the measurement result x from the true or actual value (x i or x d) of the measured quantity: xx x id. (2.1) The true value of a physical quantity is the value of a physical quantity that ideally characterizes the corresponding physical quantity qualitatively and quantitatively. It does not depend on the means of our knowledge and is an absolute truth. It can only be obtained as a result of an endless process of measurements with endless improvement of methods and measuring instruments. The actual value of a physical quantity is the value of a physical quantity obtained experimentally and so close to the true value that it can be used instead of it in the given measurement problem. Measurement errors can also be classified according to a number of criteria, in particular: a) according to the method of numerical expression; b) by the nature of the manifestation; c) according to the type of source of occurrence (causes of occurrence). According to the method of numerical expression, the measurement error can be: The absolute measurement error (x) is the difference between the measured value and the actual value of this value, i.e. x x x d. (2.2) Relative measurement error () is the ratio of the absolute measurement error to the actual value of the measured quantity. The relative error can be expressed in relative units (in fractions) or as a percentage: x or x 100%. (2.3) x x The relative error shows the accuracy of the measurement. 17
18 Depending on the nature of the manifestation, there are systematic (s) and random (0) components of measurement errors, as well as gross errors (misses). A systematic measurement error (s) is a component of the measurement result error that remains constant or regularly changes during repeated measurements of the same physical quantity. Random measurement error (0) is a component of the measurement result error, which changes randomly (in sign and value) during repeated measurements, carried out with the same care, of the same physical quantity. Gross errors (misses) occur due to erroneous actions of the operator, a malfunction of the measuring instrument, or sudden changes in measurement conditions (for example, a sudden drop in voltage in the power supply network). The following components of the total measurement error are considered depending on the type of source of error: allowed simplifications in measurements. The instrumental components of the error are errors that depend on the errors of the measuring instruments used. The study of instrumental errors is the subject of a special discipline of the theory of accuracy of measuring devices. The subjective components of the error are errors due to the individual characteristics of the observer. Errors of this kind are caused, for example, by a delay or advance in signal registration, incorrect reading of tenths of a division of the scale, asymmetry that occurs when a stroke is set in the middle between two risks, etc. Approximate estimation of the error Single measurements. The vast majority of technical measurements are single. The performance of single measurements is substantiated by the following factors: production necessity (destruction of the sample, impossibility of repeating the measurement, economic feasibility, etc.); eighteen
19 the possibility of neglecting random errors; random errors are significant, but the confidence limit of the measurement result error does not exceed the permissible measurement error. For the result of a single measurement, a single reading value of the instrument reading is taken. Being essentially random, a single reading x includes instrumental, methodological and personal components of the measurement error, in each of which systematic and random components of the error can be distinguished. The components of the error of the result of a single measurement are the errors of the measuring instrument, the method, the operator, as well as the errors due to changes in the measurement conditions. The error of the result of a single measurement is most often represented by systematic and random errors. The error of MI is determined on the basis of their metrological characteristics, which must be specified in regulatory and technical documents, and in accordance with the RD Method and operator errors must be determined during the development and certification of a specific MIM. Personal errors in single measurements are usually assumed to be small and are not taken into account. indirect measurements. With indirect measurements, the desired value of the quantity is found by calculation based on direct measurements of other physical quantities that are functionally related to the desired quantity by the known dependence y f x1, x2,..., xn, (2.4) where x1, x2,..., x n subject to direct measurements function arguments y. The result of indirect measurement is an estimate of the value of y, which is found by substituting the measured values of the arguments x i into formula (4). Since each of the arguments x i is measured with some error, the problem of estimating the error of the result is reduced to summing the errors in the measurement of the arguments. However, a feature of indirect measurements is that the contribution of individual errors in the measurement of arguments to the error of the result depends on the type of function (4). 19
20 For estimation of errors, it is essential to divide indirect measurements into linear and non-linear indirect measurements. For linear indirect measurements, the measurement equation has the form: y n bi xi, (2.5) i1 where b i are constant coefficients at the arguments x i. The result of a linear indirect measurement is calculated by formula (2.5), substituting the measured values of the arguments into it. The measurement errors of the arguments x i can be set by their boundaries xi. With a small number of arguments (less than five), a simple estimate of the error of the result y is obtained by simply summing the marginal errors (ignoring the sign), i.e., substituting the boundaries x 1, x 2, x n into the expression: y x1x2 ... xn. (2.6) However, this estimate is overestimated, since such summation actually means that the measurement errors of all arguments simultaneously have a maximum value and coincide in sign. The probability of such a coincidence is practically zero. To find a more realistic estimate, we proceed to the static summation of the error of the arguments according to the formula: n 2 2 i i, (2.7) i1 yk b x where k is the coefficient determined by the accepted confidence probability (at P = 0.9 at k = 1.0; .95 at k = 1.1, P = 0.99 at k = 1.4). Nonlinear indirect measurements any other functional dependencies other than (2.5). With a complex function (2.4) and, in particular, if it is a function of several arguments, the determination of the law of distribution of the result error is associated with significant mathematical difficulties. Therefore, the approximate estimation of the error of nonlinear indirect measurements is based on the linearization of function (2.4) and further processing of the results, as in linear measurements. Let us write the expression for the total differential of the function y in terms of partial derivatives with respect to the arguments x i: y y y dy dx1 dx2... dxn. (2.8) x x x 1 2 n 20
21 By definition, the total differential of a function is the increment of a function caused by small increments of its arguments. Considering that the measurement errors of the arguments are always small compared to the nominal values of the arguments, we can replace in formula (2.8) the differentials of the arguments dx n with the measurement error xn, and the function differential dy with the error of the measurement result y: y y y y x x... xn. (2.9) x x x If we analyze formula (2.9), we can obtain a simple rule for estimating the error of the result of a non-linear indirect measurement . Errors in works and private. If the measured values x1, x2,..., x n are used to calculate y x... 1x2 xn or y 1, x2 then the relative errors y x1x2... xn are summed, where y y. y 2.3. Recording (rounding) error of a number The recording (rounding) error of a number is defined as the ratio of half of the unit of the least significant digit of the number to the value of the number. For example, for the normal acceleration of falling bodies g \u003d 9.81 m / s 2, the unit of the least significant digit is 0.01, therefore, the error in writing the number 9.81 will be equal to 0.01 5, \u003d 0.05%. 29, Purpose of work n x development of methods for conducting single direct and indirect measurements; mastering the rules for processing, presenting (recording) and interpreting the results of measurements; acquisition of practical skills in the use of measuring instruments of different accuracy, as well as analysis and comparison of the accuracy of the results of indirect measurements with the accuracy of the measuring instruments used in direct measurements; identification of possible sources and causes of methodological errors; 21
22 consolidation of theoretical material in the section "Metrology" of the discipline under study "Metrology, standardization and certification" Equipment used vernier caliper (hereinafter SC); micrometer; ruler. When recording the measuring instruments used, indicate their normalized metrological characteristics using the measuring instruments Work program Perform single measurements of the diameter and height of the cylinder with measuring instruments of various accuracy: calipers, micrometers and rulers. Record the measurement results in the table. As cylinder 1, select a cylinder of lower height. Record the results of direct measurements of the diameter and height of the cylinders in a table with the accuracy with which the measuring instrument allows you to measure. Table 2.1 Measurement results Measured Cylinder 1 (small) Cylinder 2 (large) parameter Diameter d, mm Height h, mm Volume V, mm Rel. V Abs. error V, mm 3 micrometer ШЦ ШЦ ruler Determine the volume of the cylinder using the ratio: 2 V d h, mm 3, (2.10) 4 where = 3.14 is a numerical coefficient; d cylinder diameter, mm; h cylinder height, mm Determine the relative measurement error, expressed in relative units V V. (2.11) V 22
23 To determine the relative measurement error V, it is necessary to transform formula (2.11) into a convenient one for calculation using formula (2.9) (see section 2.2). In the resulting formula, d, h are the errors of the measuring instruments used in the measurements. In indirect measurements of physical quantities, tabular data or irrational constants are very often used. Because of this, the value of the constant used in the calculations, rounded up to a certain sign, is an approximate number that contributes its share to the measurement error. This fraction of the error is defined as the error in recording (rounding off) the constant (see clause 2.3) Determine the error in calculating the volume using the formula V V, mm 3. (2.12) V Round off measurement errors and record the result of measurements of cylinder volumes V V V mm 3. (2.13) For in order to record the final result of indirect measurements, it is necessary to round off the measurement error V in accordance with MI 1317, agree on the numerical values of the result and measurement errors (see clause 2.4) Show in the figures the areas in which the results of volume measurements obtained by different measuring instruments are located for each of the cylinders. An example is shown in Figure 2.1. V 2 ΔV 2 V 2 V 1 ΔV 1 V 1 V 1 + ΔV 1 V 2 + ΔV 2 Then you need to select the scale and put down all the other points. Show the error of the method in the figure. 23
24 2.6.7 Prepare a report and draw a conclusion (see Appendix A for an example of a title page). In the conclusion, evaluate the obtained measurement results, identify possible sources and causes of methodological errors Test questions 1. Name the main types of measurements. 2. By what criteria are measurement errors classified? 3. Name and describe the main types of measurement errors. 4. How to determine the error in writing a number? 5. How to determine the error of the result of indirect measurement? 2.8. Literature used 1. RMG Recommendations on interstate standardization. GSI. Metrology. Basic terms and definitions. 2. R Recommendations on metrology. GSI. Direct single measurements. Estimation of errors and uncertainty of the measurement result. M., Publishing house of standards, Borisov Yu.I., Sigov A.S., Nefedov V.I. Metrology, standardization and certification: textbook. Moscow: FORUM: INFRA-M, MI Guidelines. GSI. Results and characteristics of measurement errors. Submission Forms. Methods of use in testing product samples and monitoring their parameters. 24
25 LABORATORY WORK 3 PROCESSING THE RESULTS OF DIRECT MULTIPLE MEASUREMENTS 3.1. Introduction The need to perform direct multiple measurements is established in specific measurement procedures. During statistical processing of a group of results of direct multiple independent measurements, the following operations are performed: known systematic errors are excluded from the measurement results; calculating an estimate of the measurand; calculate the standard deviation of the measurement results; check for gross errors and, if necessary, exclude them; checking the hypothesis that the measurement results belong to a normal distribution; calculate the confidence limits of the random error (confidence random error) estimates of the measured value; calculate the confidence limits (boundaries) of the non-excluded systematic error in the estimate of the measured value; calculate the confidence limits of the error in estimating the measured value. The hypothesis that the measurement results belong to a normal distribution is tested with a significance level q from 10% to 2%. Specific values of significance levels should be specified in a specific measurement procedure. To determine the confidence limits of the error in estimating the measured value, the confidence probability P is taken equal to 0. Basic concepts and definitions Depending on the nature of the manifestation, systematic (C) and random (0) components of the measurement error are distinguished, as well as gross errors (misses). Gross errors (misses) arise due to erroneous actions of the operator, a malfunction of the measuring instrument, or sudden changes in measurement conditions, for example, a sudden drop in voltage in the power supply network. Closely adjoining them are the errors that depend on 25
26 observers and related to improper handling of measuring instruments. The systematic measurement error (systematic error C) is the component of the measurement result error that remains constant or regularly changes during repeated measurements of the same physical quantity. It is believed that systematic errors can be detected and eliminated. However, under real conditions, it is impossible to completely eliminate the systematic component of the measurement error. There are always some factors that need to be taken into account, and which will constitute a non-excluded systematic error. Non-excluded systematic error (NSE) is a component of the error of the measurement result, due to errors in the calculation and introduction of corrections for the influence of systematic errors or a systematic error, the correction for which is not introduced due to its smallness. Non-excluded systematic error is characterized by its boundaries. The boundaries of the non-excluded systematic error Θ with the number of terms N 3 are calculated by the formula: N i, (3.1) i1 where i-th border component of the non-excluded systematic i error. With the number of non-excluded systematic errors N 4, the calculation is carried out according to the formula k N 2 i, (3.2) i1 ; at P = 0.99, k = 1.4). Here Θ is considered as a confidence quasi-random error. Random measurement error (0) is a component of the measurement result error, which changes randomly (in sign and value) during repeated measurements, carried out with the same care, of the same physical quantity. 26
27 To reduce the random component of the error, multiple measurements are carried out. The random error is estimated by the confidence interval tp Sx, (3.3) where t P is the Student's coefficient for given level confidence probability Р d and sample size n (number of measurements). Confidence limits of the error of the measurement result of the boundary of the interval within which the desired (true) error value of the measurement result is located with a given probability. Sample a series of x measurement results (x i ), i = 1,..., n (n > 20), from which known systematic errors are excluded. The sample size is determined by the requirements of measurement accuracy and the possibility of repeated measurements. A variational series is a selection sorted in ascending order. Histogram of the dependence of the relative frequencies of the measurement results falling into the grouping intervals on their values, presented in graphical form. Estimation of the distribution law Estimation of the correspondence between the experimental distribution law and the theoretical distribution. It is carried out using special statistical criteria. When p< 15 не проводится. Точечные оценки закона распределения оценки закона распределения, полученные в виде одного числа, например оценка дисперсии результатов измерений или оценка математического ожидания и т. д. Средняя квадратическая погрешность результатов единичных измерений в ряду измерений (средняя квадратическая погрешность результата измерений) оценка S рассеяния единичных результатов x измерений в ряду равноточных измерений одной и той же физической величины около среднего их значения, вычисляемая по формуле: 1 n S 2 x x 1 i x n, (3.4) i1 где i x результат i-го единичного измерения; x среднее арифметическое значение измеряемой величины из n единичных результатов. Примечание. На практике широко распространен термин среднее квадратическое отклонение (СКО). Под отклонением в соответствии с приведенной выше формулой понимают отклонение единичных результатов в ряду измерений от их среднего арифметического значения. В метрологии это отклонение называется погрешностью измерений. 27
28 The mean square error of the measurement result of the arithmetic mean estimate S x of the random error of the arithmetic mean of the measurement result of the same value in a given series of measurements, calculated by the formula 2 i S Sx 1 x x x n nn1, (3.5) measurements obtained from a series of equally accurate measurements; n number of single measurements in a series Exclusion of gross errors To exclude gross errors, Grubbs' statistical test is used, which is based on the assumption that a group of measurement results belongs to a normal distribution. To do this, calculate the Grubbs criteria G 1 and G 2, assuming that the largest x max or smallest x min measurement result is caused by gross errors: xmax x x x G1, min S G. (3.6) x 2 Sx Compare G 1 and G 2 with the theoretical value G T of the Grubbs test at the chosen significance level q. A table of critical values of the Grubbs criterion is given in Appendix B. If G 1 > G T, then x max is excluded as an unlikely value. If G 2 > G T, then x min is excluded as an unlikely value. Next, the arithmetic mean and standard deviation of a number of measurement results are calculated again, and the procedure for checking for the presence of gross errors is repeated. If G1 G T, then x max is not considered a miss and is stored in the measurement series. If G 2 G T, then x min is not considered a miss and it is stored in a series of measurement results. The error limits for estimating the measured value (without taking into account the sign) are calculated by the formula 28
29 K S, (3.7) where K is a coefficient depending on the ratio of the random component of the error and the NSP. The total standard deviation S of the estimate of the measured value is calculated by the formula S S2 S2 x, (3.8) from formulas (3.1), or P S, (3.10) k 3 where P are the confidence limits of the NSP, which are determined by one of the formulas (3.2); k is a coefficient determined by the accepted confidence probability P, the number of NSP components and their relationship to each other. The coefficient K for substitution into formula (3.7), depending on the number of NSPs, is determined by empirical formulas respectively K, P K. (3.11) S S S x x S 3.5. Algorithm for processing the results of observations Processing of the results of observations is carried out in accordance with GOST “GSI. Measurements are direct with multiple. Methods for processing measurement results. Basic Provisions» Determination of point estimates of the distribution law x 1 n x i ; 1 n S 2 x x 1 i x n ; S S x x. n n i Construction of the experimental law of distribution of the results of multiple observations a) in Table 3.2, write the variational series of the results of multiple observations x ; i i1 29
PRACTICAL LESSON 6 "Processing the results of equal-precision measurements, free from systematic errors" The lesson is devoted to solving problems of calculating the errors of equal-precision measurements
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Federal State Budgetary Educational Institution of Higher Professional Education "Yugorsk State University" (SGU)
NIZHNEVARTOVSK OIL COLLEGE
(branch) of the federal state budgetary educational institution
higher professional education "Ugra State University"
(NNT (branch) FGBOU VPO "YUGU")
METROLOGY, STANDARDIZATION AND CERTIFICATION
Guidelines for performing laboratory work
for students of all forms of education of educational institutions of secondary vocational education.
Nizhnevartovsk 2015
TOPICS OF LABORATORY WORKS ON THE DISCIPLINE
"METROLOGY STANDARDIZATION AND CERTIFICATION"
Number
Number and name of the lesson
Number of classroom hours
form of control
1.
Laboratory work No. 1 "Measurement of parts with caliper tools"
2
2.
Laboratory work No. 2 “Measurement of parts with a micrometric tool
2
3.
Laboratory work No. 3 "Measuring parts with indicator devices"
2
4.
Laboratory work No. 4 "Measurement of the plug gauge"
2
5.
Laboratory work No. 5 "Surface roughness"
2
Lab #1
MEASURING PARTS WITH ROD INSTRUMENTS
Objective
To study the device, the principle of measurement and metrological characteristics of calipers.
Measure the given part with a caliper.
Draw a sketch of the part with actual dimensions.
ROD INSTRUMENTS
To measure linear dimensions by the absolute method and to reproduce dimensions when marking parts, caliper tools are used, which combine under this name a large group of measuring instruments: calipers, caliper depth gauges, caliper gauges, caliper gauges, etc.
The most common type of caliper is the caliper. There are several models of calipers (GOST 166-80).
Fig.1
Caliper ШЦ-Ia) for external and internal measurements and with a ruler for measuring depths (scale division of the vernier 0.1 mm, measurement limit from 0 to 125 mm) has a rod (ruler) 1 with the main scale, the divisions of which are applied through 1 millimeter. The rod has fixed double-sided measuring jaws with working surfaces perpendicular to the rod. The measuring frame moves along the ruler 2 with a second pair of sponges; there is a locking screw on the frame 4 to fix it in the desired position. An additional scale is applied on the measuring frame - vernier 3 . External dimensions are measured with lower jaws having flat working surfaces of small width. Upper jaws are used to measure internal dimensions. Ruler-depth gauge 5 designed to measure the height of ledges, the depth of blind holes, etc.Caliper ШЦ-II with bilateral arrangement of jaws (Fig. 1, b) is designed for external and internal measurements and marking work. Consists of the same main parts as ShTs-I, but has an auxiliary microfeed frame 4 for precise frame movement 1 on the bar 5 . To do this, you must first fix the auxiliary frame 4 lock screw 3 and then turning the nut 6 by microscrew 7 , move the measuring frame along the rod. As a rule, this feed is used to accurately set the size on the caliper when marking. The pointed sponges of the ShTs-II caliper are used for marking or measuring external dimensions in hard-to-reach places. The lower jaws for measuring internal dimensions have cylindrical working surfaces. The size of the jaws when flattened is usually 10 mm and defines the smallest internal dimension that can be measured with this caliper. For internal measurements, the size of the jaws indicated on their side should be added to the scale reading. Calipers type ShTs-II have verniers with a division value of 0.1 and 0.05 mm and measurement limits of 0-160, 0-200, 0-250 mm.
Caliper ШЦ-III does not have upper pointed jaws and a device for micro-feeding of the measuring frame. It is used for external and internal measurements using the same lower jaws as those of ShTs-II. The scale division of the vernier is 0.1 and 0.05 mm, the measurement limits are from 0 to 2000 mm.
Depth gauge(Fig. 2) is used to measure depths and protrusions. It consists of a base 1 , bars 6 with basic millimeter scale, measuring frame 3 , locking screw 2 , micrometric feeders 5 , locking screw 4 , nuts and screws 7 micrometric feed and vernier 8 .
Fig.2
Depth gauges are produced with a vernier scale division of 0.05 mm and measurement limits of 0-160, 0-200, 0-250, 0-315, 0-400 mm. By design, the depth gauge differs from the caliper in the absence of fixed jaws on the rod and the presence of a base instead of them. 1 , which is a reference when measuring depth. The zero size of the depth gauge shows when the end of the rod (ruler) is aligned 6 and grounds 1 .
Fig.3
Height gauge used for marking, but it can also be used to measure the height of parts installed on the plate (Fig. 3). Height gauges have a vernier scale division of 0.1 and 0.05 mm and a measurement limit of up to 2500 mm. They have a massive base 5 for installation on a stove. The bar is perpendicular to the base 1 with millimeter scale. Movable frame 2 with vernier 3 has a holder 4 for installing a special measuring foot 6 for measuring height or marking foot 7 .When marking vertical surfaces, the height gauge with the size set on the scale and vernier (in this case, it is recommended to use the microfeed of the frame) moves along the plate along the marked workpiece. The tip of the marking leg draws a horizontal line on the surface of the workpiece.
READING DEVICE
The design of the reading device is based on a rod (measuring ruler) with the main scale applied on it with a division interval of 1 mm. Every fifth division of the rod scale is marked with an elongated stroke, and every tenth division is marked with a longer stroke with the corresponding number of centimeters.
A measuring frame moves freely along the bar, on the bevel of which (opposite the millimeter scale of the bar) an additional scale, called a vernier, is applied. Nonius is used to count fractional millimeters.
The reading of measurements in a vernier device is based on the difference between the intervals of divisions of the main scale and, additionally, the vernier scale. Nonius has a small number of divisions n(10, 20 or 50 stroke divisions). The zero stroke of the vernier acts as an arrow and allows you to read the size in millimeters on the main scale.
Nonius division price With equal to the division value of the main scale a\u003d 1 mm divided by the number of divisions of the vernier scale n :
.
Nonius are used with a division value of 0.1; 0.05 mm and in rare cases 0.02 mm. Vernier division interval 
depends on the accepted modulo value 
, which is selected from the numbers 1; 2; 3; 4 or more. But it must be borne in mind that with an increase in the module, the length of the additional vernier scale increases and the overall dimensions of the entire reading device increase. Vernier division interval taken as a multiple of the division interval of the main scale
,
where - modulus of the vernier characterizing the extension of the vernier scale or the ratio between the values of the intervals of the main scale and the vernier.
Vernier scale length
For example, let's take the price of division of the vernierWith
=0.1 mm with module 
, then the division interval of the vernier scale 
mm. All subsequent strokes of the vernier are applied at the same interval. Due to the fact that the intervals of divisions of the vernier are less than on the main scale, the lag of the position of the vernier strokes from the strokes of the main scale gradually accumulates and the tenth stroke of the vernier coincides with the ninth stroke of the main scale (Fig. 4).
Fig.4
For the convenience of counting fractional millimeters, caliper tools with a vernier scale modulus equal to 2 are more often produced.
When determining the size of the part, proceed as follows. If the zero stroke of the additional vernier scale coincided with any stroke of the main scale, then the value of the measured quantity is read off only on the main scale in mm.
If the zero stroke of the vernier does not coincide with any stroke of the main scale, then the reading is obtained from two parts. An integer in millimeters is taken on the main scale to the left of the zero stroke of the vernier and a fraction of a millimeter is added to it, obtained by multiplying the division price of the vernier by the ordinal number of the stroke of the vernier scale that coincided with the stroke of the main scale (Fig. 4, b,c).
Objective.
Caliper model and its main metrological characteristics. Method of measurement.
test questions
Name the types of calipers.
Models of calipers, their design features and appointment.
How are integer and fractional fractions of millimeters counted during measurements? Nonius device.
For what purposes is the thickness of the jaws marked on some models of calipers?
What is a depth gauge used for?
What is the height gauge used for?
Literature
Lab #2
MEASURING PARTS WITH MICROMETRIC INSTRUMENTS
Objective
To study the device, the principle of measurement and the metrological characteristics of micrometric instruments.
Measure the part with a smooth micrometer and give a conclusion about the suitability of the part.
MICROMETRIC INSTRUMENTS
Micrometric instruments are widely used means of measuring external and internal dimensions, depths of grooves and holes. The principle of operation of these tools is based on the use of a screw-nut pair. A precise micrometer screw rotates in a fixed micronut. From this knot these instruments got their name.
In accordance with GOST 6507-78, the following types of micrometers are produced:
MK - smooth for measuring external dimensions;
ML - sheet with a dial for measuring the thickness of sheets and tapes;
MT - pipe for measuring the thickness of the walls of pipes;
МЗ - gear measuring for measuring the length of the common normal of gears;
MVM, MVT, MVP - micrometers with inserts for measuring various threads and parts made of soft materials;
MP, MRI - lever micrometers;
MV, MG, MN, MN2 - desktop micrometers.
In addition to the listed types of micrometers, micrometric inside gauges (GOST 10-75 and GOST 17215-71) and micrometric depth gauges (GOST 7470-78 and GOST 15985-70) are produced.
Almost all manufactured micrometers have a division value of 0.01 mm. The exception is lever micrometers MP, MP3 and MRI, which have a division value of 0.002 mm. The measurement ranges of smooth micrometers depend on the size of the bracket and are: 0-25, 25-50, ..., 275-300, 300-400, 400-500, 500-600 mm
In Fig.1, a,b the construction and scheme of a smooth micrometer are shown. In the holes of the bracket 1 pressed on one side fixed measuring foot 2 , and on the other - the stem 5 with a hole that guides the micrometer screw 4 . micrometer screw 4 screwed into the micronut 7 having cuts and external threads. A special adjusting nut is screwed onto this thread. 8 , which compresses the micronut 7 until the gap is completely selected in the “microscrew-micronut” connection. This device provides precise axial movement of the screw relative to the micronut depending on the angle of its rotation. For one revolution, the end of the screw moves in the axial direction by a distance equal to the thread pitch, i.e. by 0.5 mm. A drum is put on the micrometer screw 6 , fixed with an adjusting cap-nut 9 . A special safety mechanism is mounted in the cap-nut 12 , connecting the cap-nut 9 and ratchet 10 , for which it is necessary to rotate the drum 6 during measurements. The safety ratchet mechanism, consisting of a ratchet wheel, a tooth and a spring, in case of excess force between the jaws of 500-900 cN, disconnects the ratchet 10 from the mounting cap 9 and drum 6 , and it starts to turn with a characteristic click. In this case, the micrometer screw 4 does not rotate. To fix the screw 4 in the required position, the micrometer is provided with a locking screw 11 .
Fig.1
On the stem 5 micrometer marked scale 14 with divisions through 0.5 mm. For ease of reference, even strokes are drawn above, and odd strokes below the solid longitudinal line. 13 , which is used to count the drum rotation angles. A circular scale is marked on the conical end of the drum 15 , which has 50 divisions. If we take into account that in one revolution of the drum with fifty divisions, the end of the screw and the cut of the drum are moved by 0.5 mm, then turning the drum by one division will cause the movement of the end of the screw equal to 0.01 mm, i.e. the division price on the drum is 0.01 mm.
When taking a reading, use the scales on the stem and drum. The cut of the drum is an indicator of the longitudinal scale and registers readings with an accuracy of 0.5 mm. To these readings add a reading on the scale of the drum (Fig. 1, in).
Before measurement, the correct zero setting should be checked. To do this, it is necessary to rotate the microscrew with a ratchet until the measuring surfaces of the heel and the screw come into contact or these surfaces come into contact with the setting measure. 3 (fig.1, a).
Ratchet rotation 10 continue until a characteristic click. The correct setting is when the end of the drum coincides with the extreme left stroke of the scale on the stem and the zero stroke of the circular scale of the drum coincides with the longitudinal line on the stem. If they do not match, it is necessary to fix the microscrew with a stopper. 11 , unscrew the adjusting cap-nut by half a turn 9 , turn the drum to the position corresponding to zero, fix it with a cap-nut, release the microscrew. After that, you should once again check the correctness of the “zero setting”.
Micrometric instruments also include a micrometric depth gauge and a micrometric inside gauge.
Micrometer depth gauge(fig.2, a) consists of a micrometer head 1 , pressed into the base hole 2 . The end of the microscrew of this head has a hole where replaceable rods are inserted with split springy ends 3 with spherical measuring surface. Replacement rods have four sizes: 25; fifty; 75 and 100 mm. The dimensions between the ends of the rods are very accurate. The measuring surfaces in these devices are the outer end of the replaceable rod 3 and bottom bearing surface 2 . When taking a reading, it must be remembered that the main scale located on the stem has a reverse countdown (from 25 mm to 0).
Fig.2
To adjust the depth gauge, the supporting surface of the base is pressed against the end of a special setting measure (Fig. 2, b), which is placed on the calibration plate. The microscrew with the insert is brought to contact with the plate using a ratchet, fixed with a stopper, and then the same operations are performed as when setting the micrometer to zero.Measuring the depth of holes, ledges, undercuts, etc. perform as follows. The support surface of the base of the micrometric depth gauge is installed on the base surface of the part against which the size is measured. With one hand, the base is pressed against the part, and with the other hand, the drum of the micrometer head is rotated by the ratchet until the rod touches the measured surface and the ratchet clicks. Then the microscrew is fixed with a stopper and the reading is taken from the scales of the head. Micrometric depth gauges have measurement limits from 0 to 150 mm and a division value of 0.01 mm.
Micrometric inside gauges designed to measure the internal dimensions of products in the range from 50 to 6000 mm.
They consist of a micrometer head (Fig. 3, a), interchangeable extension cords (Fig. 3, b) and measuring tip (Fig. 3, in).
The micrometer head of the inside gauge is somewhat different from the head of the micrometer and depth gauge and does not have a ratchet. into the stem 6 the measuring tip is pressed on one side of the micrometer head 7 , and on the other, a microscrew is screwed 5 which is connected to the drum 4 nut 2 and locknut 1 . Protruding measuring tip of the microscrew 5 .
The gap in the screw-nut connection is selected using the adjusting nut 3 screwed onto a split micronut with an external conical thread. Installed size fixed with a locking screw 9 . To extend the measurement range in the threaded hole of the coupling 8 extensions are screwed in (Fig. 3, b) and measuring tip (Fig. 3, in).
Fig.3
The extension is a rod with spherical measuring surfaces that has an exact size in the axial direction. The rod does not protrude beyond the body, at both ends of which a thread is cut. A spring located inside the body creates a force closure between the rods when the extension cord is screwed together with a micrometer head. Another extension can be screwed onto the free end of the extension, etc., until an inside gauge with the required measurement limit is obtained. The measuring tip is screwed into the last extension. During the measurement process, the measuring tip of the microscrew and the measuring tip of the extension come into contact with the workpiece. When using the caliper with several extensions, it must be remembered that the extensions should be connected in descending order of their size and the micrometer head should be connected to the longest of them.
The micrometric caliper assembly with the measuring tip is set to zero according to the installation measure-bracket with a size of 75 mm (Fig. 3, G). If the zero setting is not satisfactory, loosen the locknut by half a turn. 1 , turn the drum until the zero risk coincides with the longitudinal line of the stem, tighten the lock nut 1 and release the screw 9 . Then check the correct installation. After setting the inside gauge to zero, it is screwed with extension cords to obtain the required size and measurements are started.
Measurements of internal dimensions with a caliper are carried out as follows. Insert the tool into the space between the measuring surfaces (for example, into a hole). One measuring tip of the inside gauge is installed on the surface and the head drum is rotated until the second measuring tip touches the opposite surface. During the measurement process, it is necessary not only to rotate the drum, but also to shake the assembled inside gauge, measuring the diameter in a plane perpendicular to the axis of the hole and in the plane of the axial section. The largest dimension in the first position and the smallest dimension in the second position must match.
Objective.
Design and metrological characteristics of a smooth micrometer. How are micrometer readings read during measurements?
Detail sketch with actual dimensions.
Assessment of the suitability of parts.
test questions
Types of micrometric instruments.
Micrometer device.
How to take micrometer readings? Setting the micrometer to zero.
What is a ratchet used for?
Micrometric depth gauge device.
The device of a micrometric caliper.
Literature
Markov N.N., Ganevsky G.M. Design, calculation and operation of control and measuring instruments and devices. –M.: Mashinostroyeniye, 1993.
Belkin I.M. Means of linear-angular measurements. Directory. –M.: Mashinostroenie, 1987.
Vasiliev A.S. Basics of metrology and technical measurements. –M.: Mashinostroenie, 1980.
Lab #3
MEASUREMENT OF PARTS WITH INDICATOR DEVICES
Objective
To study the device, principle of operation and metrological characteristics of the dial indicator and indicator instruments.
Get the skills of independent work with devices by measuring the details with an indicator bracket and an indicator caliper.
GEAR MEASURING HEADS
OR DIAL INDICATORS
Measuring heads are called reading devices that convert small movements of the measuring rod into large movements of the pointer along the scale (clock-type indicators, lever-toothed indicators, multi-turn indicators, lever-toothed heads).
Fig.1. Dial indicator IC-10
As a separate measuring device heads cannot be used and for measurement they are installed on racks, tripods or equipped with instruments and instrumentation.Measuring heads are designed mainly for relative measurements. If the dimensions of the parts are less than the range of the instrument readings, then the measurements can be performed by the absolute method.
The most common geared measuring heads are dial gauges.
The principle of operation of the dial indicator is as follows (Fig. 1):
Measuring rod1
moves in precise guide bushings. A toothed rack is cut on the rod, which is engaged with the tribe4
(
=16). A tribe in instrumentation is a gear wheel of a small module with the number of teeth ≤18. On the same axis with the tribe4
gear wheel installed3
(=100), which transmits rotation to the tribe2
(\u003d 10). On the same axis, the tribe2
fixed big arrow8
, which moves along the scale7
, counting tenths and hundredths of a millimeter of movement of the measuring rod with a tip12
.
When moving the measuring rod in the range of indications, the large arrow makes several turns, therefore, an additional arrow is installed in the design of the dial indicator 5 on the axis of the tribe 4 and wheels 3 . When moving the measuring rod by 1 mm, the large arrow 8 makes one revolution, and the arrow 5 moves one division of the small scale 6.
The number of divisions of the small scale determines the range of readings of dial indicators in mm.
Tribe 2
the second gear is engaged9
(=100). A spiral spring is attached to the axle of this wheel at one end.10
, the second end of which is fixed in the indicator housing. The spring ensures the operation of the gears in the mode of single-profile gearing, thereby reducing the effect of gaps in the gear pairs on the measurement error.
The dial gauge has a helical spring 11 , one end of which is fixed on the measuring rod, and the other - on the indicator body. This spring creates a measuring force on the rod R=150±60 cN.
All dial gauges have a scale interval of 0.01 mm. Most indicators have a reading range of 2 mm (IC-2), 5 mm (IC-5), 10 mm (IC-10) and indicators with a reading range of 25 mm (IC-25) and 50 mm (IC-50) are less commonly produced.
The measurement error of a dial indicator depends on the movement of the measuring rod. So in the range of readings 1÷2 mm, the measurement error is within 10÷15 µm, and in the range 5÷10mm, the error is within 18÷22 µm.
MEASURING WITH A DIAL INDICATOR
Indicator 1 mounted on an indicator stand 2 screw 3 (fig.2, a). Loosening screw 5 , lower the indicator until it touches the tip of the measuring table 4 , after which we lower it additionally by another 1 ... 2 mm (we create an “interference”). Fix this position by tightening the screw 5 . We turn the rim 6 dial of the indicator until "0" of the scale coincides with the large arrow. We write down the indicator readings (for example, 1.00 mm with an interference fit of 1 mm).
Without changing the position of the indicator housing, raise the measuring tip and place the part on the measuring table. We release the rod (Fig. 2, b) and record the indicator reading (for example, 2.15 mm) The difference between the indicator reading during measurement and during adjustment gives the value of the movement of the rod relative to the table during measurement
(b\u003d 2.15-1.00 \u003d 1.15 mm). This will be the size b. In this way, measurements are made by the absolute method.
In cases where the size of the part is greater than the range of instrument readings, the relative method is used. To do this, we determine the approximate size of the part (for example, about 42 mm), we collect a block of plane-parallel end blocks of length (also 42 mm), we set the device to "0" relative to plane-parallel end blocks of length (PKMD) (Fig. 2, in) is similar to the setting for the absolute method. We record the indicator readings (for example, 1.00 mm), remove the PKMD block and place the part. We write down the indicator readings (for example, 2.15 mm). We determine the movement of the rod when measuring relative to the PCMD ( \u003d 2.15-1.00 \u003d 1.15 mm) (Fig. 2, G). Actual part size d\u003d PKMD + (for example, d=42+1.15=43.15 mm). When adding, it is necessary to take into account the sign of the relative displacement: if the size of the part turns out to be less than the PKMD block, then will turn out to be negative. For example, if the indicator showed 1.00 mm when setting, and 0.42 mm when measuring, then
\u003d 0.42-1.00 \u003d -0.58 mm.
Fig.2. Indicator measurement
The relative method is also used in cases where it is necessary to reduce the measurement error, i.e. reduce the measuring displacement in order to get rid of the accumulating instrument error.
INDICATOR BRACKET
In the body of the bracket (Fig. 3) there is a dial indicator, a movable heel 2 and replaceable adjustable heel 3 .
Movable heel 2 is constantly pressed towards the product by the measuring rod of the indicator and a special spring. Adjustable heel 3 with screw released 4 and the removed cap can move up to 50 mm. Measurement ranges of indicator brackets are: 0÷50 mm, 50÷100 mm, 100÷200 mm, …, 600÷700 mm, 700÷850 mm, 850÷1000 mm.
The main error of the device (depending on the size of the bracket) varies from 5 to 20 microns.
MEASUREMENT WITH INDICATOR CLAMP
INDICATOR BELL GAUGE
Indicator inside gauges are designed to measure the internal dimensions and diameters of holes by the relative method.
The most commonly used inside gauges of standard sizes from the following range of measurement ranges: 6-10; 10-18; 18-50; 50-100; 100-160; 160-250; 250-450; 450-700; 700-1000 mm.
We will consider the device and operation of indicator calipers using the example of an caliper of the NI-100 model (Fig. 4).
A sleeve-insert is inserted into the body of the caliper 2 , into which a replaceable fixed measuring rod is screwed on one side 3 , and on the other side there is a movable measuring rod 4 acting on the two-arm lever 5 , fixed on the axis 6 .
A rod is placed inside the body 8 pressed against the lever 5 dial indicator stylus and coil spring 10 . The latter create a measuring force ranging from 200 to 500 cN.
Fig.4.
Within the measurement range, inside gauges are supplied with a set of interchangeable measuring rods. The position of the fixed measuring rod after adjustment is fixed with a nut 7 . Movable measuring rod 4 under the influence of the measuring force is in the extreme initial position. centering bridge 12 pressed by two springs 11 to the surface of the controlled hole, ensures the alignment of the measurement line with the diameter of the hole.
The adjustment of the inside gauge to the required nominal size is carried out using the PKMD blocks with sidewalls installed in clamp holders, or using certified rings. The error of inside gauges is usually normalized equal to 1.5 ÷ 2.5 divisions of the readout head.
MEASUREMENT WITH INDICATOR INSIDE GAUGE.
Calculate the nominal dimensions of the PMDC according to the nominal size of the hole of the measured part. Prepare an installation kit (Fig. 5) from the PMKD block, two sidewalls 2 and clamps 1 . From the set of interchangeable adjustable rods (attached to the inside gauge), select a rod with a size range in which the nominal size of the measured hole is located. Screw the replaceable adjustable rod 3 into the body of the caliper 5 .
Insert the caliper with measuring rods into the installation kit between the sidewalls and create an interference fit of 1÷2 mm for the dial indicator (Fig. 5).
Swinging the caliper from itself towards itself, turning it to the left - to the right around the vertical axis, you need to set the axis of the measuring rods (measurement axis) to a position that coincides with the smallest distance between the measuring surfaces of the sidewalls. This position will be shown by the large indicator hand when it reaches the farthest (when it moves clockwise) division of the scale and starts moving back. Having given the correct position to the indicator, it is necessary to tighten the locknut 4 interchangeable measuring rod 3 and set the zero division of the indicator scale until it coincides with the large arrow.
Fig.5. Indicator caliper when setting ( a) (centering bridge not shown)
and when measuring ( b)
After setting the inside gauge to "0", you can start measuring the deviations of the part hole size from the nominal value.
We introduce the measuring head of the caliper into the hole of the measured part. Spring-loaded centering bridge 8 orients the measuring axis of the inside gauge strictly in the diametrical plane of the measured hole (Fig. 5, b).
By swinging the caliper in a vertical plane, we determine the indicator readings at the extreme right position of the large arrow.
When determining the actual deviations of the hole sizes from the nominal, they are guided by the following rule: the deviation is accepted with a minus sign (“-”) if the large indicator needle deviates from the “0” scale division clockwise, and the counterclockwise deviation shows an increase in the diameter of the hole about the nominal size and the actual deviation is taken with a plus sign ("+").
The value of the actual deviation is calculated by multiplying the number of divisions of the indicator scale (indicated by a large arrow from "0") by the division value of 0.01 mm.
The actual size of the hole diameter will be equal to the nominal hole diameter plus ("+") or minus ("-") the actual deviation.
Objective.
Types of indicator instruments used in the work and their metrological characteristics. Method of measurement.
Sketches of measured parts with actual dimensions.
Assessment of the suitability of parts.
test questions
Design of dial gauges.
Metrological characteristics of indicator instruments. Method of measurement.
How are readings read when measuring with indicator devices?
indicator bracket. Adjustment of the clamp for measurements.
What is the name of the value that the device fixes?
Indicator caliper. Setting the caliper.
Measuring with a caliper.
Literature
Belkin I.M. Means of linear-angular measurements. Directory. –M.: Mashinostroenie, 1987.
Vasiliev A.S. Basics of metrology and technical measurements. –M.: Mashinostroenie, 1980.
Lab #4
PLUG MEASUREMENT
Objective
To study the device, principle of operation and metrological characteristics of spring measuring heads IGP - microcators (GOST 6933-81).
Get the skills of independent work with devices for accurate measurements by the relative method.
Learn how to build schemes of tolerance fields for calibers.
Measure the plug gauge with the GPI installed on the C-1 or C-2 stand.
Determine the suitability of the cork gauge.
SPRING MEASURING MICROCATOR HEADS
These devices are precision measuring devices with mechanical conversion of small movements of the measuring tip into large movements of the pointer relative to the scale of the device. This group of devices is called "spring" because the sensing element is a thin bronze ribbon curled from the middle in different directions.
14
a
b
Fig.1.
Band spring 2 fixed on a corner 1 and cantilever flat spring 4 installed on a rigid ledge (Fig. 1, a). Changing the position of the spring 4 , with the help of screws adjust the tension of the tape spring. Measuring rod 7 suspended on membranes 6 and rigidly connected to the square 1 . Moving the measuring rod causes the square to rotate around the point " a» and stretching the spring 2 . The measuring force is generated by a conical spring 5 . A quartz arrow is glued to the middle part of the bronze swirling tape 3 . Spring extension 2 causes the arrow to turn 3 relative to the scale.
Spring measuring heads are used for high-precision relative measurements of the dimensions of products, as well as deviations in the shape and location of surfaces. The accuracy of controlled products can be from 2 th until 6 th quality.
For measurements, the instruments are mounted in racks (Fig. 1, b) type C-1 and C-2 or in special devices for the tube 7 28 mm in diameter. When setting to zero position on the gauge block, microfeed of the rack table is used.
During transport, the measuring rod is clamped by turning the lock into the base of the tube.
Spring measuring heads are produced in the following modifications: 01ГП; 02IGP; 05IGP; 1IGP; 2IGP; 5IGP; 10IGP and have the price of division of the scale of the device, respectively: 0.0001; 0.0002; 0.0005; 0.001; 0.002; 0.005; and 0.01 mm.
WORK PROCEDURE
1. Study the device, the principle of measurement and the metrological characteristics of the microcator on the C-1 or C-2 rack. Record the main metrological characteristics of the device in the report (scale division of the device, measurement range on the scale of the device).
2. Get a gauge-plug for measurements from the teacher.
3. By marking on the caliber, determine which hole it is intended to test (nominal hole diameter, deviation of the hole tolerance field and quality).
4. According to GOST-25347-82 ( ST SEV 144-75) determine the maximum deviations of the size of the hole, and then build a diagram of the location of the hole tolerance field (Fig. 2)
5. According to GOST-24853-81 (ST SEV 157-75) for a given plug gauge, find tolerances, limit deviations and build a diagram of the location of the tolerance field for the gauge.
7. According to the diagram, select the size with respect to which the device is set to zero using gauge blocks.
8. From a set of plane-parallel end measures of length, take a measure or several measures to compose a block, the size of which is equal to the size selected according to the scheme.
9. End measures, rinse the instrument table with gasoline, wipe with a soft cloth. Rub the wiped measures to each other and to the table.
10. Set the instrument to zero. For this (Fig. 1, b) by releasing the locking screw 2 table 3 by turning the micrometer nut 1 , the object table with the ground block of end measures is lowered to the lower position. Then, by releasing the locking screw 10 bracket 9 , by rotating the ring-nut 11 the bracket is lowered 9 with a microcator until the tip touches the surface of the gauge block or block. The moment of contact is judged by the beginning of the movement of the arrow. In this position, the bracket 9 fixed with a screw 10 .
Attention!!!
The bracket should be lowered smoothly, avoiding the impact of the tip on the end measure! Do not touch the adjusting screws 14
table, as this will disrupt the installation
table
The final setting of the device to zero is carried out using a nut 1 ; table 3 rises until the pointer of the microcutter is aligned with the zero division of the scale. In this position, the table is locked with a screw 2 and checking the zero setting by raising and lowering the probe 4 with the help of an arrester 5 .
The exact setting of the device to zero is carried out by a screw 8 , which can shift the scale relative to the pointer within ±5 divisions.
11. By pressing the arrester, raise the measuring tip and remove the end block or block (do not disassemble the end block block).
12. Place a stopper gauge on the object stage and, pressing the gauge tightly against the stage with two fingers, slowly roll it under the tip and follow the movement of the arrow. The largest deviation of the arrow in "plus" or "minus" on the scale determines the actual deviation of the size of the plug in this section relative to the setting size of the end measure or block. To verify the correctness of the obtained deviation, the measurements are repeated two or three times. Each time there should be a clear repeatability of the tidy readings. Such measurements should be carried out in three sections along the length of the plug and in two planes (Fig. 3). Record the measurement results in the report table.
13. Determine the actual dimensions of the plug in the controlled sections, which are equal to the algebraic sum of the size of the end measure or block and the instrument reading. Record the result in a report table.
14. Check the zero reading of the instrument. To do this, by pressing the arrester, the caliber is removed from the table and the end measure or block is again installed under the measuring tip. Raising and lowering the tip two or three times, make sure that the arrow is set to zero.
The deviation of the arrow from the zero stroke should not exceed half the division of the instrument scale, if the deviation is greater, then you need to repeat the adjustment of the instrument to zero and measure the caliber.
The obtained data on the results of measurements are recorded in the report.
1. The purpose of the work.
2. The name of the measuring device and its main metrological characteristics (measurement limits on the scale of the device, scale division value).
3. The type of caliber that is controlled and its marking.
Fig. 4. Scheme of tolerance fields for the product and caliber with limiting dimensions in mm and deviations in microns (Fig. 2).
Fig.2
5. Select a gauge block or gauge block to set the instrument to zero.
6. Caliber measurement scheme (Fig. 3) and measurement results with filling in the table.
Fig.3.
Measurement results
Gauge block dimensions
or block
passing side
R-PR
impassable side
R-NOT
Sections
Sections
Indications
instrument in µm
Plane
II-II
Actual caliber dimensions in mm
Plane
II-II
7. Conclusion on the suitability of the caliber.
test questions
Device, principle of operation and metrological characteristics of spring heads-microcators.
What is the scope of microcators.
Measuring method and microcator setting for measurements.
How are the tolerance fields of smooth limiting plug gauges and staple gauges located on the diagrams?
Why is it necessary to use measuring instruments such as microcator to assess the suitability of a cork gauge?
How is the conclusion on the suitability of the caliber formulated?
Literature
Belkin I.M. Means of linear-angular measurements. Directory. –M.: Mashinostroenie, 1987.
Vasiliev A.S. Basics of metrology and technical measurements. –M.: Mashinostroenie, 1980.
Lab #5
SURFACE ROUGHNESS
Objective
To study the main parameters of roughness and the designation of roughness in the drawings.
To get acquainted with the methods of measurement and devices for assessing the surface roughness of machine parts.
BASIC CONCEPTS
Surface roughness is a set of surface irregularities with relatively small steps, selected using the base length (GOST 25142-82).
base length 
- the length of the baseline used to highlight the irregularities that characterize the surface roughness.
The numerical values of the surface roughness are determined from a single base, which is taken as the middle line of the profilem
, i.e., a base line that has the shape of a nominal profile and is drawn so that, within the base length, the standard deviation of the profile to this line is minimal. Estimation Length 
-
the length at which the real profile is evaluated. It may contain one or more base lengths. (Fig. 1).
Rice. 1. Profile and main parameters of surface roughness
NORMALIZED ROUGHNESS PARAMETERS
Roughness parameters in the direction of the height of the roughness. Arithmetic mean profile deviation 
- arithmetic mean of the absolute values of profile deviations within the base length:
or approximately 
,
where - base length; 
- number of selected profile points on the base length;y -
the distance between any point on the profile and the midline. It is normalized from 0.008 to 100 microns.
Height of profile irregularities by ten points 
-
the sum of the average absolute values of the heights of the five largest protrusions of the profile and the depths of the five largest depressions of the profile within the base length:
,
where 
-
heighti
-th largest protrusion of the profile; 
- depthi
th largest depression of the profile.
The greatest height of the profile irregularities 
- the distance between the line of the protrusions of the profile and the line of the depressions of the profile within the base length . Normalized from 0.025 to 100 microns.
Roughness parameters in the direction of the profile length. Average step of profile irregularities 
- arithmetic mean step of profile irregularities within the base length:
,
whereP -
number of steps within base length ;
-
the step of the profile irregularities is equal to the length of the segment of the middle line intersecting the profile at three adjacent points and bounded by two extreme points. It is normalized from 0.002 to 12.5 mm.
The average step of the local protrusions of the profile 
- arithmetic mean step of local protrusions of the profile within the base length:
,
where P -
number of steps of irregularities along the vertices within the base length ; 
- step of profile irregularities along the tops of the protrusions. It is normalized from 0.002 to 12.5 mm.
Numerical values of roughness parameters , , , and are given in GOST 2789-73, and in Appendix 1 the values \u200b\u200bof the base length are indicated recommended for parameters , , .
Roughness parameters related to the shape of profile irregularities. Reference profile length 
-
the sum of the lengths of the segments 
cut off at a given levelR
%
in the profile material by a line equidistant to the midlinem
-
m
and within the base length (Fig. 1).
-
the ratio of the reference length of the profile to the base length:
.
Reference profile length determined at the level of the profile sectionR,
those. at a given distance between the line of the protrusions of the profile and the line intersecting the profile equidistantly from the line of the protrusions of the profile. Profile ledge line - a line equidistant from the midline passing through the highest point of the profile within the base length. Profile section level valueR
count along the line of protrusions and choose from a number of: 5; ten; fifteen; twenty; 25; thirty; 40; fifty; 60; 70; 80; 90% off . Relative profile reference length
assigned from row 10; fifteen; twenty; 25; thirty; 40; fifty; 60; 70; 80; 90%.
The Interstate Council for Standardization, Metrology and Certification has amended GOST 2.309-73 "Surface Roughness Designations" and set the deadline for the introduction of changes - from January 1, 2005.
The changes concern both the designation of surface roughness and the rules for applying them to the drawing.
Interstate standard GOST 2.309 fully complies with ISO 1302.
1. Designation of surface roughness
Surface roughness is indicated on the drawing for all surfaces of the product performed according to this drawing, regardless of the methods of their formation, except for surfaces whose roughness is not due to design requirements.
Fig.2.
The structure of the designation of surface roughness is shown in Fig.2. When a sign is used without indicating the parameter and method of processing, it is depicted without a shelf.In the designation of surface roughness, one of the signs shown in Fig. 3 is used. Height 
should be approximately equal to the height of the digits of the dimension numbers used in the drawing. Height 
equal to (1.5…5) . The thickness of the lines of signs should be approximately equal to half the thickness of the solid main line used in the drawing. In the designation of surface roughness, the processing method of which is not established by the designer, the sign is used according to Fig. 3,a
. In the designation of surface roughness, which should be formed only by removing a layer of material, use the sign according to Fig. 3,b
. In the designation of the surface roughness, which should be formed without removing a layer of material, the sign according to Fig. 3 is used,in
indicating the value of the roughness parameter.
The surfaces of a part made from a material of a certain profile and size, which are not subject to additional processing according to this drawing, must be marked with a sign according to Fig. 3, in without specifying the roughness parameters. The condition of the surface marked with such a sign must comply with the requirements established by the relevant standard or technical specifications, or another document, and this document must be referenced, for example, in the form of an indication of the material grade in column 3 of the main inscription of the drawing according to GOST 2.104-68.
Fig.3.
The value of the roughness parameter according to GOST 2789-73 is indicated in the roughness designation after the corresponding symbol, for example: 
0,4; 6,3; 0,63; 
70; 0,032; 
50. In the example 70 indicates the relative reference length of the profile \u003d 70% at the level of the profile section 
=50%.
. The thickness of the sign lines should be approximately equal to half the thickness of the solid main line.
The type of surface treatment is indicated in the designation of roughness only in cases where it is the only one applicable to obtain the required surface quality (Fig. 5).
It is allowed to use a simplified designation of surface roughness with an explanation of it in the technical requirements of the drawing according to the example shown in Fig.6.
2. Rules for applying roughness designations
surfaces on drawings
The designations of surface roughness in the image of the product are placed on the contour lines, extension lines (as close as possible to the dimension line) or on the shelves of leader lines. It is allowed, if there is not enough space, to place the designation of roughness on the dimension lines or on their extensions, on the shape tolerance frame, and also to break the extension line (Fig. 7).
Fig.7
Fig.8
Fig.9
The designations of the surface roughness in which the sign has a shelf are placed relative to the main inscription of the drawing as shown in Figures 8 and 9. When the surface is located in the shaded zone, the designation is applied only on the leader line shelf.
When specifying the same roughness for all surfaces of the product, the roughness designation is placed in the upper right corner of the drawing and is not applied to the image (Fig. 10). The dimensions and thickness of the lines of the sign in the roughness designation, rendered to the right top corner drawing, should be approximately 1.5 times larger than in the symbols printed on the image. a-c), and for globoid worms and wheels associated with them - on the line of the calculated circle (Fig. 14, G).
The designation of the surface roughness of the thread profile is applied according to general rules with a profile image (Fig. 15, a), or conditionally on extension line to indicate the size of the thread (Fig. 15, b - e), on the dimension line or on its continuation (Fig. 15, e).
If the roughness of the surfaces forming the contour must be the same, the roughness designation is applied once in accordance with Fig. 16. Auxiliary sign diameter- 4…5 mm. In the designation of the same roughness of surfaces, smoothly passing one into another, the sign 
Fig.16
Fig.17
Fig.18
Wherein letter designation surfaces are applied on the shelf of the leader line drawn from the thickened dash-dotted line, which circles the surface at a distance of 0.8 ... 1.0 mm from the contour line (Fig. 18).
SURFACE ROUGHNESS MEASUREMENT AND CONTROL
Surface roughness certification is carried out according to two types of control: qualitative and quantitative.
Quality control of surface roughness parameters is carried out by comparison with samples or exemplary parts visually or by touch. GOST 9378-75 establishes roughness samples obtained by machining, removing positive prints by electroforming or coating plastic prints. Sets or individual specimens have straight, arcuate, or criss-cross arcuate arrangements of surface irregularities. Parameter value is indicated on each sample (in µm) and type of sample processing. To improve accuracy, probes and comparison microscopes are used.
Quantitative control of roughness parameters is carried out by non-contact and contact measuring instruments.
To quantify surface roughness by a non-contact method, two methods are used - increasing them using an optical system or using the reflectivity of the treated surface.
Devices based on the assessment of surface irregularities when they are enlarged with the help of an optical system are "light section devices". Reflectivity-based instruments are microinterferometers.
The principle of operation of light section devices is to obtain an enlarged image of the profile of the measured surface using rays directed obliquely to this surface, and to measure the height of irregularities in the resulting image. The most common is a double microscope type MIS-11, which allows you to determine three parameters of roughness with the fact that many of the functional units they have the same. These instruments are mainly intended for use in the laboratory. Domestic industry manufactures several models of devices (201, 202, 252) based on the inductive method of converting needle vibrations into voltage fluctuations.
A profilograph is a device for recording the values of surface irregularities in a section normal to it in the form of a profilogram, the processing of which determines all parameters characterizing the surface roughness and waviness.
A profilometer is a device for measuring surface irregularities in a section normal to it and presenting the measurement results on the instrument scale as a value of one of the parameters used to evaluate these irregularities. Most profilometers give an estimate of surface irregularities in terms of the parameter and are used as workshop equipment. Roughness evaluation by parameter associated with signal processing difficulties.
Profile drawing of surface irregularities with basic parameters.
Estimation of roughness parameters for a given profile.
Instruments for assessing surface roughness on machine parts.
An example of the designation of roughness in the detail drawing.
test questions
What parameters are used to evaluate surface roughness?
What and how to control the surface roughness?
What roughness parameter is measured by the MIS-11 instrument?
How is roughness indicated on the drawings?
Why do they achieve low roughness on critical machine parts?
Literature
Markov N.N., Ganevsky G.M. Design, calculation and operation of control and measuring instruments and devices. –M.: Mashinostroyeniye, 1993.
Belkin I.M. Means of linear-angular measurements. Directory. –M.: Mashinostroenie, 1987.
Vasiliev A.S. Basics of metrology and technical measurements. –M.: Mashinostroenie, 1980.
This collection of descriptions of practical and laboratory work on the discipline "Metrology, standardization and certification" was developed for students in the specialties 150411, 240401, 220301, 140613. Tasks for practical work compiled in accordance with the current program, taking into account the specifics of each specialty. The collection includes works that make it possible to analyze the structure and content of standards, conduct measurements and their mathematical processing, study standardization in the industrial sector, the basic norms of product interchangeability in order to ensure its quality and competitiveness. The collection includes works to get acquainted with the basic norms of product interchangeability and standardization of GVC accuracy; on the conversion of non-metric units of measurement to SI units. It deals with questions on the choice of measuring instruments and how they measure linear dimensions.
Due to the lack of literature on the discipline, the main theoretical material necessary for studying during practical work is placed in the manual. This material is worked out independently in preparation for practical work and is fixed during its implementation. To improve theoretical and practical knowledge, the collection includes control questions and business situations.
The methodological guide includes:
Assignments to the topics of classes with an indication of the order of their implementation;
As an appendix to the collection of tasks are:
1. Law of the Russian Federation "On ensuring the uniformity of measurements";
2. the federal law"On technical regulation";
3. NSS standards: GOST R 1.0-2004, GOST R 1.12-2004, GOST R 1.2-2004, GOST R 1.4-2004, GOST R 1.5-2004, GOST R 1.9-2004, GOST 2.114-95.
4. GOST R certification system
5. Fragments of the ESDP standards.
6. Answers to tasks with a solution.
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On the topic: methodological developments, presentations and notes
Questions for the test on the subject "Metrology, standardization, certification in public catering in the profession "Technology of products o/p"" (correspondence department)
Questions for the test on the subject "Metrology, standardization, certification in public catering in the profession "Technology of products o / p"" (correspondence department) ...
METHODOLOGICAL INSTRUCTIONS FOR LABORATORY WORKS ON THE DISCIPLINE "METROLOGY, STANDARDIZATION AND CERTIFICATION"
The guidelines are intended for performing laboratory work in the sub-discipline "Metrology, standardization and certification", contain information on the arrangement and control methods of a universal machine...
METHODOLOGICAL INSTRUCTIONS for the implementation of practical work in the discipline Metrology, standardization and certification for full-time and part-time students
The guidelines were developed on the basis of the Federal State Educational Standard in the specialty 190631 Maintenance and repair of medium-sized motor vehicles ...
Practical work on the discipline "Metrology, standardization, certification and technical documentation""
in the discipline "Metrology, standardization, certification and technical documentation"...
Guidelines for independent work on the discipline "Metrology, standardization and certification"
The methodology for studying the modern course of metrology, standardization and quality assurance involves the use of students' work aimed at self-acquisition and replenishment of knowledge ...
The textbook discusses the means and methods of carrying out work on various types of standardization and certification. Scientific-technical, normative-methodical and organizational bases of standardization and certification of production and services are stated. In order to harmonize work in the field of standardization and certification, the methodology and practice of certification abroad are considered in detail. A large number of examples and reference data are given in the form of tables and diagrams. After each chapter are given control questions and tasks.
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