VLAC-VR103-Second Edition

Guideline for Traceability of Measurement

Date of Issue: December 19, 2002

Voluntary EMC Laboratory Accreditation Center, Inc. (VLAC)

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VLAC-VR103-Second Edition

Guideline for Traceability of Measurement Introduction This document is prepared by that Voluntary EMC Laboratory Accreditation Center (hereinafter called this Center) for a part of evaluation on accreditation of testing laboratory of Electromagnetic Compatibility (EMC) testing sphere. This document is based on VLAC-VR101 (General requirements for the Laboratory Accreditation) (ISO/IEC 17025 version) article 5.6 (Traceability of measurements) and giving an aspect to conduct specific operation and is not beyond compass of general requirements. 1. Applicable Scope This document is defined that relevant test laboratory ensure traceability of their test facilities when the test laboratory needs to obtain accreditation to perform electromagnetic compatibility (EMI test and Immunity test) as a competent test laboratory. 2. Normative references 2.1Quoted standards VIM: 1993 (International Vocabulary of Basic and General Terms in Metrology) ISO/IEC17025:1999 General requirements for the competence of calibration laboratory and testing laboratory VLAC VR101: General requirements for the Laboratory Accreditation GUM: 1993 2.2 Related standards VCCI-VT001: Guideline for antenna calibration VCCI- V3: Agreement of Voluntary Control Council for Interference by Information Technology Equipment Normative Annex 1 Technical Requirements VLAC-VR104: Technical Requirements for calibration and inspection of measurement equipment. 3. Definition of Terms 3.1 Traceability The property of a result of a measurement whereby it can be related to appropriate standards, generally international or national standards, through an unbroken chain of comparisons in which all uncertainties are indicated(VIM: 1993) 3.2 Calibration The set of operations which establish under specified conditions, the relationship between values indicated by a measuring instrument or measuring system, or values represented by a material measure or reference material and the corresponding known values of a measurand (VIM:1993) 3.3 Measurement Set of operations having the object of determining the value of a quantity（reference: VIM:1993) 3.4 Uncertainty of measurement Parameter associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand. For example an estimate which characterizes the range of values within the true value (VIM: 1993, GUM: 1993) 3.5 Test A technical operation that consists of the determination of one or more characteristics of a given product, process or service according to a specified procedure.

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VLAC-VR103-Second Edition 3.6 Verification Confirmation by examination and provision of evidence that specified requirements have been met. 3.7 Reference Standard A standard, generally of the highest metrological quality available at a given location or within an organization from which measurements made at that location are derived (VIM-6.6). 4．Basic Policy 4.1 General Testing laboratory shall monitor if all test facilities, test equipment, and reference standards give significantly affecting the precision of test results and its effectiveness. Concerning the items that affect the test results, the test laboratory shall establish calibration plan and procedure. Calibration and verification shall be done before use and these records shall be held.. Reference 1 Calibration plan should include a system for selecting, using, calibrating, checking, controlling and maintaining measurement standards, reference standards used as measurement standards and measuring and test equipment used to perform tests and calibrations. Comment 1 Calibration certificates or records of calibrations shall contain a statement that these equipments for the measurement, test facilities or reference standards are traceable national standards. In addition, these shall contain measurement results to include uncertainty of measurement. This explanation on uncertainty of measurement should be basically based on the guide of the explanation (GUM). Comment 2 Concerning relevant equipment, calibration services with calibration certificates etc. which conform to comment 1 are not performed but if the verification can be available, the laboratory shall attach expanded information (such as criteria of tolerance etc.) which can obtain results same as comment 1 and the information will be treated as its records 4.2 Calibration As far as test laboratories can not ascertain that contributing rate of calibrations to entire uncertainty of test results is just a little, test facilities utilizing measurement facilities and measurement function shall be applied to following required items., a) Calibration plan of equipment shall be designed and operated to be traceable to the Systèmes International d'Unités (called SI units hereinafter) of measurement. b) National measurement standards may be primary standards, which are primary realizations of the units of the SI or agreed representations of SI units based on fundamental physical constant or they may be secondary standards which are standards calibrated by another national measurement institute, c) In case of using external calibration services, traceability of measurements shall be assured by the use of calibration services from laboratories that can demonstrate competence, measurement capability and traceability. d) The calibration certificates issued by these laboratories shall contain the measurement uncertainty and/or a statement of compliance with an identified measurement specification. e) Where calibration can not be made in SI units, traceability shall be established as follows. -The use of specified methods and/or consensus standards that are clearly described and agreed by all parties concerned. Where possible, participation in a suitable program of interlaboratory comparisons is required. Reference: 1. Traceability to SI units of measurements may be achieved by reference to an appropriate primary standard (see VIM:1993,6.4 ) or by reference to a natural constant the value of which in terms of the relevant SI unit is known and recommended by the General Conference of Weight 3

VLAC-VR103-Second Edition and Measures(CGPM) and the International Committee for Weights and Measures(CIPM) 2. When the terms “international standard” or “national standard” are used in connection with traceability, it is assumed that these standards fulfill the properties of primary standards for the realization of SI units. 3. Traceability to national measurement standards does not necessarily require the use of the national measurement institute of the country in which the laboratory is located, 4. The unbroken chain of calibrations or comparisons may be achieved in several steps carried out by different laboratories that can demonstrate traceability. 4.3 Testing Testing laboratory shall ensure that uncertainty of measurement on used facilities is adequate. 4.4 Records that demonstrate appropriateness How to carry out calibrations (including obtaining equivalent results by using verification) is varied from characteristics, degree of precision (uncertainty) of testing performed by testing laboratories. Testing laboratories themselves have to identify and control these equipments to meet intended purpose and there are many different kinds of record formats. Followings are the required guideline for records of calibration of test equipment. 4.4.1 Calibration with calibration certificate that include necessary information a) Calibrations by JCSS (Japan Calibration Service System) Calibration certificates with logo mark by JCSS accredit laboratory group within accreditation. b) Calibrations by National Standards Research such as Independent Administrative Agency: National Institute of Advanced industrial Science and Technology Communications Research Laboratory and Japan Electric Meters Inspection Corporation, JCSS Accredited Laboratory Group c) Calibrations by Calibration Laboratory accredited by calibration accredit scheme other than JCSS. d) Calibrations by other calibration laboratories In such case to use following calibration certificates, these shall be traceable to SI units. In other words, calibrated value and uncertainty of calibration shall be appended as results of calibrations and these shall be proven to acquire traceability to national standards that is primary standards to achieve SI units. ・ Calibration certificates issued out of accreditation by JCSS Accredited Laboratory Group ・ Calibration certificates issued by suppliers of measurement facilities/test equipment In this case, the agency who issued calibration certificates are needed to have sufficient Quality System and technical competence to perform relevant calibrations, and the test laboratories to utilize the calibration certificates shall confirm it and record the matters. e) Internal calibration A testing laboratory that performs calibrations shall have requirements for calibration agency. In other words, test laboratories are needed to have all related records (for example budget sheet on uncertainty etc.) including calibration records and estimation of uncertainty of measurements performed by appropriately trained staff, using reference standards or facilities etc to be traceable , according to the documented procedure, 4.4.2 Verification 4.4.2.1 Point of concern in case of use of verification In a lot of cases, measurement data and uncertainty of measurement are not notified in the results of official tests.( Proficiency certificate, Certification mark etc) Therefore, in these cases not notified , the laboratory is needed to obtain the Expanded information.

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VLAC-VR103-Second Edition 5. Interim procedure Concerning the National Measurement Standards (especially derived unit) which are unfilled quantities of units, the testing laboratory shall calibrate their test equipment according to following alternate procedure as transient period until the relevant national standards are supplied. 5.1 Antenna Calibration 5.1.1 Testing Laboratories shall request antenna calibration to national measurement standard agency or to agency (calibration laboratory) who supplies standards to be traceable to national measurement standard agency. 5.1.2 Testing Laboratories that maintain their own standards of derived unit and calibrate according to these standards shall follow items described below.. a) Basic quantities of derived unit shall be traceable to the national standards. b) Testing laboratories shall document establishment method for their own standards for derived unit and clarify the calibration procedures. In addition, concerning establishment of standards, if the uncertainty can be calculated, it should be recorded. c) In order to ascertain externality of value established above, if there is another testing laboratory that establishes the same kind of standards, interlaboratory comparison between relevant testing laboratories should be performed. d) As there are a lot of items that are not clarified technically concerning antenna calibration (antenna factor, antenna impedance), antenna calibration shall conform to VCCI-VT001 (Guideline for antenna calibration) for a time.

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