测量仪器校准间隔的确定指南 英文版.pdf

GUIDANCE ILAC-G24 INTERNATIONAL OIML D 10SERIES Edition 2007(E)DOCUMENT Edition 2007(E)ORGANISATION INTERNATIONALEDE METROLOGIE LEGALE INTERNATIONAL LABORATORY ACCREDITATION COOPERATION INTERNATIONAL ORGANIZATIONOF LEGAL METROLOGY Guidelines for the determination of calibration intervals of measuring instruments Guide pour la dtermination des intervalles de calibration des instruments de mesure ILAC-G24:2007/OIML D 10:2007(E)2 CONTENTS Copyright ILAC.3 Foreword OIML.4 Preamble.5 Purpose.5 Authorship.5 1.Introduction.5 2.Initial choice of calibration intervals.7 3.Methods of reviewing calibration intervals.7 Method 1:Automatic adjustment or“staircase”(calendar-time).8 Method 2:Control chart(calendar-time).8 Method 3:“In-use”time.9 Method 4:In service checking,or“black-box”testing.9 Method 5:Other statistical approaches.9 Bibliography.11 ILAC-G24:2007/OIML D 10:2007(E)3 Copyright(ILAC)ILACG24:2007 Copyright ILAC 2007 ILAC encourages the authorized reproduction of its publications,or parts thereof,by organizations wishing to use such material for areas related to education,standardization,accreditation,good laboratory practice or other purposes relevant to ILACs area of expertise or endeavor.Organizations seeking permission to reproduce material from ILAC publications must contact the ILAC Chair or Secretariat in writing or via electronic means such as e-mail.The request for permission should clearly detail:1)the ILAC publication,or part thereof,for which permission is sought;2)where the reproduced material will appear and what it will be used for;3)whether the document containing the ILAC material will be distributed commercially,where it will be distributed or sold,and what quantities will be involved;4)any other background information that may assist ILAC to grant permission.ILAC reserves the right to refuse permission without disclosing the reasons for such refusal.The document in which the reproduced material appears must contain a statement acknowledging ILACs contribution to the document.ILACs permission to reproduce its material only extends as far as detailed in the original request.Any variation in the stated use of the ILAC material must be notified in advance in writing to ILAC for additional permission.ILAC shall not be held liable for any use of its material in another document.Any breach of the above permission to reproduce or any unauthorized use of ILAC material is strictly prohibited and may result in legal action.To obtain permission or for further assistance,please contact:The ILAC Secretariat c/o NATA PO Box 7507 Silverwater NSW 2128 Australia Fax:[phone] E-mail:ilacnata.asn.au ILAC-G24:2007/OIML D 10:2007(E)4 Foreword(OIML)The International Organization of Legal Metrology(OIML)is a worldwide,intergovernmental organization whose primary aim is to harmonize the regulations and metrological controls applied by the national metrological services,or related organizations,of its Member States.The main categories of OIML publications are:?International Recommendations(OIML R),which are model regulations that establish the metrological characteristics required of certain measuring instruments and which specify methods and equipment for checking their conformity.OIML Member States shall implement these Recommendations to the greatest possible extent;?International Documents(OIML D),which are informative in nature and which are intended to harmonize and improve work in the field of legal metrology;?International Guides(OIML G),which are also informative in nature and which are intended to give guidelines for the application of certain requirements to legal metrology;and?International Basic Publications(OIML B),which define the operating rules of the various OIML structures and systems.OIML Draft Recommendations,Documents and Guides are developed by Technical Committees or Subcommittees which comprise representatives from the Member States.Certain international and regional institutions also participate on a consultation basis.Cooperative agreements have been established between the OIML and certain institutions,such as ISO and the IEC,with the objective of avoiding contradictory requirements.Consequently,manufacturers and users of measuring instruments,test laboratories,etc.may simultaneously apply OIML publications and those of other institutions.International Recommendations,Documents,Guides and Basic Publications are published in English(E)and translated into French(F)and are subject to periodic revision.Additionally,the OIML publishes or participates in the publication of Vocabularies(OIML V)and periodically commissions legal metrology experts to write Expert Reports(OIML E).Expert Reports are intended to provide information and advice,and are written solely from the viewpoint of their author,without the involvement of a Technical Committee or Subcommittee,nor that of the CIML.Thus,they do not necessarily represent the views of the OIML.This publication-reference ILAC-G24/OIML D 10,Edition 2007-was developed by the ILAC Accreditation Committee and by OIML TC 4 Measurement standards and calibration and verification devices.This version supersedes OIML D 10(Edition 1984).It was approved for final publication by ILAC in November 2005 and by the International Committee of Legal Metrology in 2002.OIML Publications may be downloaded from the OIML web site in the form of PDF files.Additional information on OIML Publications may be obtained from the Organizations headquarters:Bureau International de Mtrologie Lgale 11,rue Turgot-75009 Paris-France Telephone:[phone] Fax:[phone] E-mail:bimloiml.org Internet:www.oiml.org ILAC-G24:2007/OIML D 10:2007(E)5 Guidelines for the determination of calibration intervals of measuring instruments Preamble This Guidance Document is a revision of OIML D 10.It was drafted by ILAC(International Laboratory Accreditation Cooperation)and the OIML(International Organization of Legal Metrology)as a joint venture and is published as such.It is important to point out that:It is not the responsibility of accreditation bodies to teach laboratories how to run their business.It is the responsibility of each individual laboratory to choose to implement any or none of the methods described in this Document based on its individual needs and its individual assessment of risks.It is also the responsibility of the laboratory to evaluate the effectiveness of the method it chooses to implement and take responsibility for the consequences of the decisions taken as a result of the method chosen.Purpose The purpose of this Document is to give laboratories,particularly while setting up their calibration system,guidance on how to determine calibration intervals.This Document identifies and describes the methods that are available and known for the evaluation of calibration intervals.Authorship This publication was developed by the OIML and ILAC as a joint venture and as a revision of OIML D 10.Within ILAC the focal point has been the Accreditation Committee.1.Introduction An important aspect for maintaining the capability of a laboratory to produce traceable and reliable measurement results is a determination of the maximum period that should be permitted between successive calibrations(recalibrations)of the reference or working standards and measuring instruments used.Various international standards take this aspect into account,e.g.:ISO/IEC 17025:2005 1 contains the following requirements:Clause 5.5.2:“Calibration programs shall be established for key quantities or values of the instruments where these properties have a significant effect on the results”.Clause 5.5.8:Whenever practicable,all equipment under the control of the laboratory and requiring calibration shall be labeled,coded,or otherwise identified to indicate the status of calibration,including the data when last calibrated and the date or expiration criteria when recalibration is due”.Clause 5.6.1“All equipment used for tests and/or calibrations,including equipment for subsidiary measurements(e.g.for environmental conditions)having a significant effect on the accuracy or validity of the result of the test,calibration or sampling shall be calibrated before being put into service.The ILAC-G24:2007/OIML D 10:2007(E)6 laboratory shall have an established program and procedure for the calibration of its equipment.”Note:Such a program should include a system for selecting,using,calibrating,checking,controlling and maintaining measurement standards,reference materials used as measurement standards,and measuring and test equipment used to perform tests and calibrations.ISO 9001:2000 10 contains the requirement:Clause 7.6:“Where necessary to ensure valid results,measuring equipment shall:a)be calibrated or verified at specified intervals,or prior to use,against measurement standards traceable to international or national measurement standards;where no such standards exist,the basis used for calibration or verification shall be recorded”.Note:This Document focuses on the determination of calibration intervals of measuring instruments.The methods described can also be used in an appropriate manner for reference standards,working standards,etc.,which are under the control of the laboratory.In line with the terminology of the VIM 11,the term“measuring instrument”is used instead of“measuring equipment”in this Document.The general purpose of a periodic calibration is:to improve the estimation of the deviation between a reference value and the value obtained using a measuring instrument,and the uncertainty in this deviation,at the time the instrument is actually used;to reassure the uncertainty that can be achieved with the measuring instrument;and to confirm whether or not there has been any alteration of the measuring instrument which could introduce doubt about the results delivered in the elapsed period.One of the most significant decisions regarding the calibration is“When to do it”and“How often to do it”.A large number of factors influence the time interval that should be allowed between calibrations and should be taken into account by the laboratory.The most important factors are:uncertainty of measurement required or declared by the laboratory;risk of a measuring instrument exceeding the limits of the maximum permissible error when in use;cost of necessary correction measures when it is found that the instrument was not appropriate over a long period of time;type of instrument;tendency to wear and drift;manufacturers recommendation;extent and severity of use;environmental conditions(climatic conditions,vibration,ionizing radiation,etc.);trend data obtained from previous calibration records;recorded history of maintenance and servicing;frequency of cross-checking against other reference standards or measuring devices;frequency and quality of intermediate checks in the meantime;transportation arrangements and risk;and degree to which the serving personnel are trained.ILAC-G24:2007/OIML D 10:2007(E)7 Although the cost of calibration cannot normally be ignored in determining the calibration intervals,the increased measurement uncertainties or a higher risk in terms of measurement quality and services arising from longer intervals may mitigate against the apparently high cost of a calibration.The process of determining calibration intervals is a complex mathematical and statistical process requiring accurate and sufficient data taken during the calibration process.There appears to be no universally applicable single best practice for establishing and adjusting the calibration intervals.This has created a need for better understanding of the calibration interval determination.As no single method is ideally suited for the whole range of measuring instruments,some of the simpler methods of assigning and reviewing the calibration interval and their suitability for different types of instruments are covered in this Document.The methods have been published in more detail in certain standards(e.g.2),or by reputable technical organizations(e.g.5,6,7),or in relevant scientific journals.The methods can be used for the initial selection of calibration intervals and the readjustment of these intervals on the basis of experience.Laboratory-developed methods or methods adopted by the laboratory may also be used if they are appropriate and if they are validated.The laboratory should select appropriate methods and should document those used.Calibration results should be collected as historical data,in order to base future decisions for calibration intervals of the instruments.Independently from the determined calibration intervals,the laboratory should have an appropriate system to ensure the proper functioning and calibration status of the standards and measuring instruments used between calibrations(see Clauses 5.5.10 and 5.6.3.3 of ISO/IEC 17025:2005).2.Initial choice of calibration intervals The initial decision in determining the calibration interval is based on the following factors:the instrument manufacturers recommendation;expected extent and severity of use;the influence of the environment;the required uncertainty in measurement;maximum permissible errors(e.g.by legal metrology authorities);adjustment of(or change in)the individual instrument;influence of the measured quantity(e.g.high temperature effect on thermocouples);and pooled or published data about the same or similar devices.The decision should be made by a person or by persons with general experience of measurements,or of the particular instruments to be calibrated,and preferably also with knowledge of the intervals used by other laboratories.An estimate should be made for each instrument or group of instruments as to the length of time the instrument is likely to remain within the maximum permissible error after calibration.3.Methods of reviewing calibration intervals Once calibration on a routine basis has been established,adjustment of the calibration intervals should be possible in order to optimize the balance of risks and costs as stated in the introduction.It will probably be found that the intervals initially selected do not give the desired optimum results due to a number of reasons,for example:instruments may be less reliable than expected;the usage may not be as anticipated;it may be sufficient to carry out a limited calibration of certain instruments instead of a full calibration;and ILAC-G24:2007/OIML D 10:2007(E)8 the drift determined by the recalibration of the instruments may show that longer calibration intervals may be possible without increasing risks,etc.A range of methods is available for reviewing the calibration intervals.The method chosen differs according to whether:instruments are treated individually or as groups(e.g.by manufacturers model or by type);instruments exceed the calibration by drift over time or by usage;instruments show different types of instabilities;instruments undergo adjustments;and data are available and importance is