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1 COMMITTEE DRAFT ISO/CD COMMITTEE DRAFT Date Supersedes document -- Reference number ISO/TC 213 N 760 WARNING: This document is not an International Standard. It is distributed for review and comment. It is subject to change without notice and may not be referred to as an International Standard. ISO/TC 213 Title Dimensional and geometrical product specifications and verification Secretariat DS Circulated to P- and O-members, and to technical committees and organizations in liaison for: discussion at [venue/date of meeting] comments by [date] approval for registration as a DIS in accordance with of part 1 of the ISO/IEC Directives, by [date] (P-members vote only: ballot form attached) P-members of the technical committee or subcommittee concerned have an obligation to vote. Title (English) Geometrical Product Specifications (GPS) Dimensional measuring instruments; Height gauges Design and metrological requirements Part 1: Simple height gauges Title (French) Spécification géométrique des produits (GPS) Instruments de mesurage dimensionnel; Mesureurs verticaux Spécification de conception et spécifications métrologiques Partie 1: Reference language version: English French Russian Introductory note According to ISO/TC 213 Resolution 728, this draft has been submitted to CD ballot for comments and approval within ISO/TC 213. Copyright notice This ISO document is a committee draft and is copyright protected by ISO. While the reproduction of committee drafts in any form for use by participants in the ISO standards development process is permitted without prior permission from ISO, neither this document nor any extract from it may be reproduced, stored or transmitted in any form for any other purpose without prior written permission from ISO. Requests for permission to reproduce this document for the purpose of selling it should be addressed to the secretariat indicated above or to ISO s member body in the country of the requester. Reproduction for sales purposes may be subject to royalty payments or a licensing agreement. Violators may be prosecuted. ISO 2005 All rights reserved FORM 7 (ISO) Version/V97.1.2

2 ISO ISO for CD Geometrical Product Specifications (GPS) Dimensional measuring instruments; Height gauges Design and metrological requirements Part 1: Simple height gauges Spécification géométrique des produits (GPS) Instruments de mesurage dimensionnel; Mesureurs verticaux Spécification de conception et spécifications métrologiques Contents 1 Scope Normative references Terms and definitions Design characteristics General design and nomenclature Dimensional characteristics and conception Types of indicating devices Metrological characteristics General Effect of measuring head locking Maximum permissible errors of indication of linear dimension Repeatability for probing Hysteresis Instrument specification sheet Proving of conformance with specification Marking... 9 Annex A (informative) Error tests Annex B (informative) Data sheet (example) Annex C (informative) Relation to the calibration Annex D (informative) Relation to the GPS matrix model Bibliography page Copyright notice This ISO document is a Draft International Standard and is copyright-protected by ISO. Except as permitted under applicable laws of the user's country, neither this ISO draft nor any extract from it may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, photocopying, recording or otherwise, without written permission being secured. Requests for permission to reproduce should be addressed to ISO at the address below or ISO's member body in the country of requester. Copyright Manager ISO Central Secretariat 1 rue de Varembé 1211 Geneva 20 Switzerland tel fax Internet central@isocs.iso.ch Reproduction may be subject to royalty payments or a licensing agreement. Violators may be prosecuted.

3 Foreword ISO for CD ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental or non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75% of the member bodies casting a vote. ISO was prepared by the Technical Committee ISO/TC 213, Dimensional and geometrical product specifications and verification. Annex C is for information only. Introduction This International Standard is a geometrical product specification (GPS) standard and is to be regarded as a general GPS standard (see ISO/TR 14638). It influences the chain link 5 and 6 of the chain of standards on size, distance, form of line independent of datum and orientation. For more detailed information of the relation of this standard to the GPS matrix model see annex C. This standard is intended to serve the purpose of promoting: - the relationship between manufacturer and purchaser; - the management of measuring instruments in the quality assurance system. Reference to the general standard on measurement equipment ISO 14978

4 Geometrical Product Specifications (GPS) Dimensional measuring instruments; Height gauges Design and metrological requirements Part 1: Simple height gauges ISO for CD 1 Scope This International Standard specifies the most important design and metrological characteristics of height gauges - for linear-dimensional measurements perpendicular to a reference surface - with analogue indication: vernier scale or circular scale ( dial) - with digital indication: digital display. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this International Standard. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain registers of currently valid International Standards. ISO 1:2002, Standard reference temperature for industrial length measurements ISO 463: 1, Geometrical Product Specifications (GPS) Dimensional measuring instruments; Dial gauges Design and metrological requirements ISO 1101:1985 1, Technical drawings Geometrical tolerancing - Tolerancing of form, orientation, location and run-out Generalities, definitions, symbols, indications on drawings ISO 3650:1998, Geometrical Product Specifications (GPS) Length standards Gauge blocks ISO :1990, Surfaces plates - Part 2: Granite ISO : 1, Geometrical Product Specifications (GPS) Dimensional measuring instruments; Callipers and depth gauges Design and metrological requirements ISO : 1, Geometrical product specifications (GPS) Inspection by measurement of work pieces and measuring equipment Part 1: Decision rules for proving conformance or non-conformance with specification ISO/TR : 1, Geometrical product specifications (GPS) Inspection by measurement of work pieces and measuring equipment Part 1: Guide to the estimation of uncertainty in GPS measurement, in calibration of measuring equipment and in product verification ISO 14978: 1, Geometrical product specifications (GPS) General concepts and requirements for GPS measuring equipment VIM:1993, International Vocabulary of Basic and General Terms in Metrology 1) Under preparation 3

5 3 Terms and definitions For the purpose of this International Standard, the terms and definitions given in ISO 14978, VIM and the following apply. 3.1 Simple height gauge Measuring instrument which measures a distance based on height measurements made perpendicular to a reference surface on the instrument base. NOTE Most height gauges are capable of moving on a reference surface e.g. on a surface plate. 4 Design characteristics 4.1 General design and nomenclature Current simple height gauges use mechanical contact with the reference surface. Large or heavy simple height gauges may use air bearings, for example, to move the instrument on the reference surface. Key 1 Instrument base 7 Fixing device 2 Guiding column 8 Measuring and scribing stylus 3 Guiding face 9 Main scale 4 Fine adjustment device 10 Vernier scale 5 Measuring head 11 Clamping screw 6 Probe extension 12 Reference surface Figure 1 Vernier height gauge with analogue indication The specific design of the simple height gauges illustrated on figure 1 shall only be seen as example. Simple height gauges do not necessarily correspond to the figure 1 above. Many other detailed designs exist. 4

6 4.2 Dimensional characteristics and conception Characteristics Base length L 1 width L 2 Global dimensions Air bearings distance L 1 distance L 2 mm system diameter D 1 diameter D 2 Air pressure p bar Column total height TH measuring range MR Probing system measuring distance min MD min measuring distance max MD max mm Fixing devices Protection For scriber, type For dial gauge, type For dial test indicator, type Fluid or dust IP code Electromagnetic field protection Yes/No Yes/No Yes/No 4.3 Types of indicating devices Several types of indicating devices are possible: - analogue indicating devices with vernier scale or circular scale (see figures 2 and 5) - digital indicating devices with digital display (see figure 6). On instruments with analogue indicating devices the scales interval and its unit shall be labelled. On instruments with a digital indicating device the unit of the indication shall be labelled Analogue indicating devices The scale interval of the main scale on the beam of an instrument with vernier scale shall be specified. The main scale shall be longer by at least one vernier scale length than the measuring range of the instrument. In the case of instruments with circular scales, the scale interval on the beam may be greater than 1 mm. 5

7 Main scale and vernier scale Key 1 Main scale 2 Vernier scale Figure 2 Analogue indication with main and vernier scale Design of vernier scale Indicating Device main scale on the guiding column and vernier scale on the chamfered surface of the measuring head. See figure 3. Indicating Device main scale on the column guide and vernier scale on the plain surface of the measuring head (parallax-free-reading). See figure 4. Graduating methods of verniers: - vernier scale interval 0,1 mm divide 19 mm into 10 equal parts - vernier scale interval 0,05 mm divide 39 mm into 20 equal parts - vernier scale interval 0,02 mm divide 49 mm into 50 equal parts Scale surfaces Common types of scale surfaces on the slider see figure 4 and 5. Key 1 Guiding column 3 Main scale 2 Measuring head 4 Vernier scale Figure 3 Standard measuring head with vernier scale NOTE The height difference between the edges of the vernier scale surface and the main scale surface should be as small as possible, for example 0,3 mm. 6

8 Key 1 Guiding column 3 Main scale 2 Measuring head 4 Vernier scale Figure 4 Measuring head with vernier scale for reading without parallax error NOTE The main scale surface and vernier scale surface shall be nominally at the same level and the distance between the main scale and the vernier scale should be as small as useful Main scale and circular scale Main scale on the guiding column and circular scale on the measuring head. The circular scale shall be graduated in scale intervals. The scale interval and its unit shall be labelled. Key 1 Main scale 2 Circular scale Figure 5 Scale reading with circular scale Digital indicating device Instruments with an electronic digital display may also be capable of data transfer. In this case the manufacturer shall describe the data output protocol (interface) in sufficient details. The manufacturer shall indicate the electrical power consumption. Key 1 Digital display 2 Electronic main scale Figure 6 Electronic main scale on the beam, digital indication on the measuring head 7

9 4.3.3 Protection for field use Manufacturers shall express clearly which kind of fluid, dust (IP code according to IEC 60529), and electromagnetic field protection is given or not Probing system The probing system may include a rigid probe or any sort of indicating probe. The stylus of the probe system may be interchangeable for various measurements. The fixing device shall accept extension for to fix other measuring instrument e.g. dial gauge Instrument base The instrument's base shall be designed in such a manner that safe upright positioning and easy movement of the measuring instrument on the surface plate are guaranteed; it shall also ensure that the measuring instrument cannot slide alone across the surface plate. The instrument base shall be designed to prevent tilting when travelling over the tapped holes or slots on the measuring surface. Figure 7 Main dimensions from the air bearings system 5 Metrological characteristics 5.1 General Instruments with an analogue indicating device can have a fixed zero point or can be capable of being set to zero in any position within the measuring range MR (see figure 1). Instruments with a circular scale can be capable of being set to zero within the range of the dial scale. Instruments with a digital display can be capable of being set to zero in any position within the measuring range. The following clauses define the detailed metrological characteristics of a height gauge. Verification of the metrological characteristics to the MPE-values stated by the manufacturer shall be performed according to Annex C. Rated operating conditions: If not otherwise stated by the manufacturer the rated operating conditions are at a temperature 20 C with the gauge placed on a flat reference surface. Some instruments have the possibility of software compensation of the temperature influence; consequently, the rated operating temperature conditions for these instruments may be a larger range. 8

10 The manufacturer shall indicate the thermal coefficient of linear expansion so the user can convert the measured values to the standard reference temperature of 20 C (see ISO 1). NOTE The temperature coefficient of the measuring instrument mainly results from the coefficient of linear expansion of the guiding column as well as the material measure, e.g. scale or rack. 5.2 Effect of measuring head locking If the measuring head is locked (in the case the measuring head is equipped with a locking device), the dimension, which is set, shall not change and the indication shall fulfil the following: - instruments with analogue indication: the indication shall not change more than one scale interval, - instruments with digital indication: the indicated value shall not change more than one digital step. NOTE The digital display may change by one digital step if the measuring head is positioned just short of the position where the indication will change. 5.3 Maximum permissible errors of indication of linear dimension (limited by MPEs) The manufacturer provide the detailed characteristics and conditions of use of the probing system(s) which will allow the maximum permissible errors (MPEs) to be respected within the measuring range (see figure 1). The detailed characteristics of a probing system may be e.g.: dimensions relative to the reference system (i.e. MD min or MD max (see figure 1) and stylus tip radius). The requirements on the error of indication apply to any indication based on the zero setting stated in 5.1 These requirements apply independently of the measuring range of the instrument. The error of indication shall not be greater than the maximum permissible errors MPE D 1 and MPE D 2 as stated as limits on the position of the path of the stylus tip with contact point as defined in table 2. NOTE The limits of permissible error may be greater than the digital step or the scale interval. Table 2 Position of the path of the stylus tip with contact point for MPE D 1 to MPE D 2 Maximum permissible error MPE D 1 MPE D 2 Distance to the reference plane M min M max Stylus tip radius r = mm NOTE M min and M max are the distances from the reference plane at which MPE D 1 and MPE D 2 are specified. The error of indication D for measurement of linear dimension is defined as measurement error over a specified dimension L. Concerning the presentation of the maximum permissible errors of indication for linear dimension measurement see clause 7.5 of ISO The manufacturer shall state the detailed conditions for the given MPE D -function i.e. the values of the constants a, b and, if necessary, for c. The detailed conditions are: - fixed or floating zero; in case of fixed zero the zero-point must be clearly defined, - measuring volume as a total or the special location(s) in the measuring volume, - direction(s) of travel and direction(s) of measuring force (i.e. unidirectional step-height (distance) measurements (two directions of travel and two directions of measuring force) or bidirectional size measurements (external and/or internal size) in case of linear dimension measurements), - probing system and its position relative to the measuring head. 9

11 5.4 Repeatability for probing The repeatability for probing R of a height gauge is specified in terms of the standard deviation of indications at any point - by unidirectional probing - on the symmetry plane. See clause 6.1 of ISO For the probing system that includes an electrical switching or measuring probe, the maximum permissible repeatability MPE R shall be stated by the manufacturer. The manufacturer shall state the detailed conditions for the given MPE R. 5.5 Hysteresis Hysteresis of a height gauge is specified in terms of the mean and standard deviation of the differences between the indications caused by a change in the direction of travel at any point in the measuring range. See clause of ISO Instrument specification sheet Each type of instrument has a specification sheet, which is intended to supply the necessary minimum information to the user. The manufacturer shall specify the values of the maximum permissible errors and tolerances and shall give information about design requirements. According to ISO/DIS clause MPE S shall be given as a continuous function (e.g. straight lines connecting defined points with the coordinates) see ISO/DIS clause for model. The table 3 give the necessary minimum information. Table 3 Maximum permissible errors (MPE) of indication Indicated value Maximum permissible error of indication Repeatability, hysteresis, scale interval and digital step MPE D 1 MPE D 2 mm µm µm Repeatability Hysteresis Scale interval Digital step MPE R.µm MPE HM...µm MPE HS.µm mm mm

12 6 Proving of conformance with specification For proving of conformance and non-conformance with specifications ISO applies. Uncertainty evaluation shall be performed according to ISO/TS and GUM. 7 Marking The marking shall indicate at least the following data: - the name or trade mark of the manufacturer/ supplier, - the vernier or dial gauge scale interval (only for analogue indication), - the unique alphanumeric identification (i.e. serial number). 11

13 Annex A (informative) A.1 Test methods The method should evaluate the performance of the equipment throughout its measuring range and/or volume. The stated specifications (MPE-values), given by the manufacturer, apply in any position or point in space throughout the entire measuring range or measuring volume or in special locations, stated as part of the detailed conditions for the various MPE-values. In practice only a limited number of measurements and points in space are used in the verification processes. These reductions in numbers do not reduce the stated requirement in any respect, but may increase the uncertainty of the resulting measurement results and therefore may influence the possibility of proving conformance and non-conformance with specification (see ISO ). Generally a specification is verified, when it can be proved, that the resulting error is less than the stated MPEvalue taking into account the actual uncertainty of measurements by the principles and rules in ISO Observe: Because the instrument shall conform to the stated requirements in all points in the measuring range and/or volume, it is a basic principle the customer has the right to choose the points of measurement during verification inside the stated measuring range and/or volume. The detailed procedure of verification therefore shall vary and shall in each case balance the effort to the actual needs. The verification methods given below shall consequently be outlines only. Details as e.g. number of points in space, number of measurements performed in each point, sort of standards, quality of standards etc. is to be decided based on the actual needs and uncertainty investigations (see ISO/TR ). A.2 Errors of indication for measurement of linear dimension Compliance with the stated MPE D shall be verified by measurements using material measures (standards) e.g. gauge blocks (see ISO 3650), step gauges or other suitable standards. The measurement procedures, the probing system and the treatment of the measurement results shall be in accordance with and derived from the detailed conditions given for the actual MPE D (see 5.4) As a guideline - based on experience - a reduced procedure may include (see clause A.1 and 5): - Determine the error of indication D in 10 points within the measuring range for travel in both directions (if possible with the stated probe system and standards), - Repeat the determination of D for one value of L for the evaluation of the repeatability for D - Repeat the measurements of D in the 10 points. The number of 10-point series of measurement depending on the repeatability of D a number of times based on one value of L - and the closeness of D in all points to the actual MPE D and taking into account the actual uncertainty of measurement. Most often less than 4 series of measurement is sufficient for proving conformance or non-conformance with the specification (see clause 7). A.3 Repeatability for probing Compliance with the stated MPE R (or MPE RH and MPE RV ) shall be verified by repeated probing of a nominal flat and smooth surface as a standard. The standard may be a gauge block (see ISO 3650) or other suitable standards with a sufficient surface quality. The measurement procedures, the probing system and the treatment of the measurement results shall be in accordance with and derived from the detailed conditions given for the actual MPE R (or MPE RH and MPE RV ) (see 5.5). The most extreme points in the stated measuring range or the measuring volume usually have the poorest repeatability. Consequently the specification preferably shall be tested and verified in these points. 12

14 As a guideline - based on experience - a reduced procedure may include (se clause A.1 and 5): ISO for CD - Determine the (statistical) range R (or RH and RV) in the extreme points of the stated measuring range or measuring volume, - The number of points and number of repeated measurements in each point depending on the closeness of R (or RH and RV) to the actual MPE R (or MPE RH and MPE RV ). Most often a sufficient number of points is between 2 and 4 and a sufficient number of repeated measurements - in each point - in the order of 10 (see clause 7). A.4 Hysteresis Compliance with the stated MPE H (or MPE HH and MPE HV ) shall be verified by probing in the same point with two directions of travel using the surface of a suitable material standard (e.g. gauge block in case of vertical hysteresis and straightness standard). For HV and MPE HV in some cases measurement data from error of indication for measurement of linear dimension can be used to derive the vertical hysteresis HV. For HH and MPE HH the measurement set-up used for straightness or perpendicularity can be used to derive the horizontal hysteresis HH. The measurement procedures and the treatment of the measurement results shall be in accordance with and derived from the detailed conditions given for the actual MPE H (or MPE HH and MPE HV ) (see 5.6). The hysteresis usually will vary between different points in the measuring range or measuring volume. No general method exists to predict where to look in the measuring volume for the largest hysteresis, if previous data do not exist. As a guideline - based on experience - a reduced procedure may include (see clause A.1 and 5): - Use 3 points, position close to the extremes (2 points) and one the middle of the measuring range. A.5 Measuring force The measurement procedures, the probing system and the treatment of the measurement results shall be in accordance with and derived from the detailed conditions given by the manufacturer (see and 5.3). The measuring force can be determined using a force standard of a suitable design. The measuring force is transmitted by the probe element at the switch point or in the centre of the measuring range depending on the system used, which can be either an electrically switching, a mechanical or electrical measuring system. 13

15 Annex B (informative) Data sheet (Example) Name of equipment Detailed requirements: (e.g. type of operating conditions, type of indicating devices, probing system, ) Accessories: Possible suppliers: Delivery requirements: (e.g. inspection report, calibration certificate) The design and metrological characteristics refer to the International Standard ISO Design characteristics Measuring range Limiting conditions Need of an air pressure source mm Effective coefficient of temperature expansion (optional) Price range (optional): Metrological characteristics Scale interval/digital step vertical: mm horizontal: mm Measuring force minimum vertical: N horizontal: N maximum vertical: N horizontal: N Maximum permissible errors (MPE) of indication Linear dimension MPE D 1 MPE D 2 Repeatability MPE R Hysteresis MPE HM MPE Hs Organisation: Department: Person responsible: Date: Signature: 14

16 Annex C (informative) Relation to the calibration C.1 Calibration of metrological characteristics The methods shall evaluate the performance of the instrument within its measuring range. The global calibration of each scale point or each digital step over the measuring range will necessitate a large number of readings to be taken. When it is considered that the intended use of the instrument does not warrant global calibration, partial calibration or task related calibration should be taken into consideration. For the determination of the errors of indication E D a suitable number of intervals, which are independent on the scale interval or digital step, the measuring range and the used measuring range, are necessary. The value of maximum permissible errors MPE S can be calculated according ISO/DIS It is possible to perform a modified global calibration by using a suitable sampling technique but this will result in an increase in the uncertainty of measurement. C.1.1 Measurement standards for the calibration of metrological characteristics Gauge blocks according to ISO 3650 and other measuring equipment according to their appropriate standards. 15

17 Annex D (normative) Relation to the GPS matrix model For full details about the GPS matrix model see ISO/TR D.1 Information about the International Standard and its use The International standard provides the most important design and metrological characteristics of simple height gauges - for lineardimensional measurements - with analogue indication: vernier scale or circular scale (dial) - with digital indication: digital display D.2 Position in the GPS matrix model This International standard is a general GPS standard, which influences the chain link 5 and 6 of the chain of standards on size, distance, form of line independent of datum and orientation in the General GPS matrix, as graphically illustrated on figure C.1. GLOBAL GPS STANDARDS FUNDAMENTAL GPS STANDARDS GENERAL GPS MATRIX Chain link number Size Distance Radius Angle Form of line independent of datum Form of line dependent of datum Form of surface independent of datum Form of surface dependent of datum Orientation Location Circular run-out Total run-out Datums Roughness profile Waviness profile Primary profile Surface imperfections Edges Figure C.1 D.3 Related standards The related standards are those of the chains of standards indicated in figure C.1. 16

18 Bibliography [1] ISO/TR 14638:1995, Geometrical Product Specifications (GPS) Masterplan [2] GUM:1995, Guide to the expression of uncertainty in measurement 17