1、BRITISH STANDARD BS 4358:1968 Glossary of Terms used in air gauging with notes on the techniqueBS4358:1968 This British Standard, having been approved by the InstrumentIndustry Standards Committee and endorsed by the Chairman of the Engineering Divisional Council, was publishedunder the authority of
2、the General Council on 27 September 1968 BSI 02-2000 The following BSI references relate to the work on this standard: Committee references INE/1/1/6, INE/1 Draft for comment D65/11472 ISBN 0 580 00334 5 Co-operating organizations The Instrument Industry Standards Committee, under whose supervision
3、this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: British Clock and Watch Manufacturers Association British Electrical and Allied Manufacturers Association* British Industrial Measuring and Control A
4、pparatus Manufacturers Association* British Nautical Instrument Trade Association British Railways Board British Scientific Instrument Research Association* British Steel Industry* Council of British Manufacturers of Petroleum Equipment* Electrical Research Association Electricity Council, the Centr
5、al Electricity Generating Board and the Area Boards in England and Wales Electronic Engineering Association Engineering Equipment Users Association* Gauge and Tool Makers Association* Institution of Chemical Engineers* Institution of Electrical Engineers* Institution of Heating and Ventilating Engin
6、eers Institution of Mechanical Engineers Institution of Production Engineers Ministry of Defence, Air Force Department* Ministry of Defence, Army Department* National Coal Board National Physical Laboratory (Ministry of Technology)* Oil Companies Materials Association* Scientific Instrument Manufact
7、urers Association* Water Resources Board Water-tube Boilermakers Association* The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of th
8、is standard: Institute of Measurement and Control Institution of Gas Engineers Ministry of Defence, Navy Department Individual Manufacturer Amendments issued since publication Amd. No. Date CommentsBS4358:1968 BSI 02-2000 i Contents Page Co-operating organizations Inside front cover Foreword ii Gene
9、ral introduction 1 1 General 6 2 Air gauge units 9 3 Measuring heads for dimensional measurement 10 4 Measuring heads for the inspection of form and position 12 Appendix A Examples of air gauging techniques for checking common errors of form and position 14 Appendix B Other applications of air gaugi
10、ng 28 Index 30 Figure 1 Displacement-flow transducer 1 Figure 2 Displacement flow-transducer with flowmeter 1 Figure 3 Displacement-pressure transducer 2 Figure 4 Contact gauging element 2 Figure 5 Examples of air gauging applications 4 Figure 6 Measurement of diameter 5 Figure a 26 Figure b 26 Figu
11、re c 26BS4358:1968 ii BSI 02-2000 Foreword This standard makes reference to the following British Standard: BS 308, Engineering drawing practice Part 3: Geometrical tolerancing using ISO symbols 1) . This British Standard has been prepared under the authority of the Instrument Industry Standards Com
12、mittee and is based upon a glossary drawn up by a group of British manufacturers of air gauging systems. Since its introduction some thirty years ago the use of the air gauging method of dimensional measurement has grown enormously in Great Britain. Not surprisingly, the terminology relating to the
13、method has become confused; terms have been invented without regard to their etymology and often with no thought as to their relationship to similar or corresponding terms in other technologies. This glossary aims at removing this confusion. During its preparation, the following objectives were kept
14、 in mind: i) to rationalize the terminology by choosing suitable terms which manufacturers would agree to use, and thus eliminate the present confusion arising from the use of different terms by different manufacturers; ii) to provide users, and potential users, of air gauging equipment with an unam
15、biguous means for communicating their requirements to manufacturers; iii) to furnish for this particular technology a terminology which finds general acceptance and becomes, in due course, the recognized terminology in the literature and in discussions of the air gauging method. In the introduction
16、to the glossary the principles of air gauging are briefly described and examples are given of the application of the method to the measurement of dimensions and the inspection of form; some notes are included on the operating pressures used. Section1 of the glossary defines the general terms relatin
17、g to the air gauging technique, whilst Section2 deals specifically with the air gauge unit, that part of the air gauging system which contains the indicating unit and the controls. In Section3, the measuring heads for dimensional measurement are detailed, and the related terms and their definitions
18、are given, whilst Section4, in conjunction with Appendix A, provides corresponding information for measuring heads employed in the inspection of form and position. Appendix B covers applications of air gauging not included in Section3, Section4 and Appendix A. A British Standard does not purport to
19、include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, p
20、ages i and ii, pages1 to 30, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) In course of preparation.BS4358:1968 BSI 02-2000 1 General int
21、roduction If the tube A which terminates in the jet J (Figure 1) is connected to a source of compressed air held at constant pressure, air will flow through the jet to atmosphere at a constant rate. If now the surface S is moved toward the jet the escape of air will be impeded and the flow will begi
22、n to decrease. Continued advancement of the surface will steadily reduce the flow until finally, with the surface in contact with the whole area of the jet, the flow ceases. This simple device is thus a displacement-flow transducer which permits detection of the movement of the surface normal to the
23、 jet by observing the change in air flow. In Figure 2, a regulator R maintains the incoming air supply at a constant pressure and a variable-area flowmeter F measures the flow of air through the jet. The float responds to the changes in flow, rising as the flow increases and falling as it decreases.
24、 The flowmeter can be graduated in units of length to give a scale which can be used to measure the displacement of the surface S normal to the jet. Figure 1 Displacement-flow transducer Figure 2 Displacement flow-transducer with flowmeterBS4358:1968 2 BSI 02-2000 It is not, however, essential to me
25、asure directly the changes in air flow: these changes can be converted into changes in air pressure by the method shown inFigure 3. A restriction O, called the control orifice, is introduced between the regulator and the jet, and the air pressure between this restriction and the jet is measured by a
26、 suitable pressure indicator G. The indicator (shown inFigure 3 in simple diagrammatic form) will register a lower pressure when the air flow through the jet increases, a higher pressure when it decreases; as before, the scale of the indicator can be graduated in units of length and used for gauging
27、. The arrangement shown inFigure 3 is thus a displacement-pressure transducer. These then are the basic ideas of air gauging. Their simplicity will be appreciated, but what is important is that they can be used to build robust measuring instruments of extremely high accuracy and stability for use in
28、 precision engineering. Their magnification, that is the ratio of the movement of the indicator index,e.g.the float inFigure 2 or the pointer inFigure 3, to the movement of the surface which produces it, can be relatively low, say, 1000, or very high, say, 100000. Magnifications of 10000 and 20000 a
29、re common and permit accurate inspection of closely-toleranced components; the true sizes of the components are obtained and errors of form and position can be investigated. The air gauging system thus offers substantial advantages over inspection by limit gauging and furthermore can, when required,
30、 be used for selective assembly of mating components. The actual gauging element, the jet inFigure 2 and Figure 3, can be separated from the indicator (flowmeter or pressure indicator) by suitable hose connexion, so that remote reading can be readily arranged. The open jet of Figure 2 or Figure 3, w
31、hich never makes contact with the work being gauged and which may, therefore, be described as a non-contact gauging element, is suitable for many applications of air gauging. For others, e.g. when measuring components which have a relatively rough surface finish or porous surfaces, it is better to u
32、se a contact gauging element. Figure 3 Displacement-pressure transducer Figure 4 Contact gauging elementBS4358:1968 BSI 02-2000 3 This may take one of several forms, but the principle is shown inFigure 4. The contact gauging element provides a stylus which is in contact with the work being gauged an
33、d it will be seen how movement of the stylus changes the flow of air. An air gauging system comprises essentially an air gauge unit and a measuring head. The air gauge unit contains the means to display the measured sizes, or to generate signals based upon them, and certain other elements depending
34、on its type; in particular, when the variable measured is pressure, it will contain the control orifice. The measuring head may contain a single gauging element, either contact or non-contact, or two or more such elements. The form of the measuring head and the number of gauging elements used will d
35、epend upon the type of measurement (length or thickness, internal diameter, external diameter, straightness, squareness, etc.) to be made. The air supply for the air gauging system will usually be drawn from the factorys compressed air line but, if necessary, a suitable local compressor may be emplo
36、yed. The air gauging system must be operated at a constant pressure; this is readily done by using a pressure regulator, which is usually provided in the air gauge unit. It is essential that the supply pressure is significantly greater than the operating pressure and the manufacturers directions sho
37、uld be observed. Systems using flow measurement normally operate at0.7bar. 2)The operating pressures in systems using pressure measurement range up to4.1bar and it is convenient to classify these systems as low, medium and high by subdivision as follows: It is important that the air supplied to the
38、air gauge unit is clean and dry and, in particular, free from oil mist. Filters should be regularly drained and periodically cleaned; attention to this point will ensure trouble-free service for a long time; but neglect will inevitably lead to a breakdown. The air gauging principle shown inFigure 2
39、andFigure 3 furnishes a means for comparing the sizes of like objects; in other words an air gauging system is a comparator and, as with all other comparators, requires standardization before it can give true size. Suitable setting standards are therefore required for use with the system and are emp
40、loyed, in conjunction with simple controls, for datum setting and for fixing the magnification. In some cases, it is convenient to fix the magnification by using master setting jets which are substituted for the measuring head. However precise the instrument used in measuring, it cannot give the cor
41、rect answer if a poor inspection technique is employed. Change of temperature alters the size of components being measured; difference of form between standard and component, or errors of form in the component, may lead to false results, and so on. The need to use sound techniques is common to all m
42、ethods of measurement; it is not to be neglected when the air gauging method is employed. Some of the more direct applications of air gauging are illustrated in the simple line drawings ofFigure 5 andFigure 6, in which the gauging element is represented by an arrow head thus. 2) 1 bar = 10 5N/m 2 .
43、Operating pressure Classification Not greater than 0.3 bar low Greater than 0.3 bar but less than 1 bar medium 1 bar and above highBS4358:1968 4 BSI 02-2000 In the examples ofFigure 5, a single gauging element is used; the measurement of length or thickness is depicted at a, that of diameter at b an
44、d depth at c; checking for squareness is shown at d and e and for straightness at f. Figure 5 Examples of air gauging applicationsBS4358:1968 BSI 02-2000 5 In the examples inFigure 6, two or more gauging elements are used for measuring diameter, the last example showing how several gauging elements
45、can be disposed so as to measure average diameter. Since it is the purpose ofFigure 5 and Figure 6 to show as clearly as possible how the air gauging method is applied, the illustrations have been confined to simple applications. One of the outstanding features of the method is its extreme flexibili
46、ty and, in consequence, its very wide field of application. It is particularly valuable for the simultaneous inspection of several dimensions, and can be conveniently employed on the machine tool to give measurement during production. Signal retainers and signal inverters can readily be incorporated
47、 in some systems; measurements can be recorded or converted into electrical signals for automatic control. All these techniques are straightforward and in everyday use. For further information on the theoretical aspects of air gauging reference should be made to “Notes on Applied Science No. 34” “Pr
48、inciples of Pneumatic Gauging” by J. C. Evans and I. G. Morgan published by H.M.S.O. (1964). Figure 6 Measurement of diameterBS4358:1968 6 BSI 02-2000 1 General No. Term Definition 1001 air gauging PNEUMATIC GAUGING, deprecated A precise measuring technique, using air drawn from a compressed air sup
49、ply, which can be employed to measure size, or to check form or position. NOTEThe technique can be based on the determination of air flow or alternatively the determination of air pressure. In either case, the measured sizes are displayed on indicators; in the latter they may alternatively or simultaneously be recorded, converted into audible or visual signals, or into signals for automatic operations,e.g.inspection, grading, control of size. 1002 air gauging system Measuring equipment employing air gauging based on the determination of
