NABL 164
NABL
NATIONAL ACCREDITATION BOARD FOR TESTING AND CALIBRATION LABORATORIES
GUIDELINES for
INTER-LABORATORY COMPARISON FOR CALIBRATION LABORATORIES WHERE FORMAL PT PROGRAMMES ARE NOT AVAILABLE
ISSUE NO : 01 ISSUE DATE: 28.04.2005
AMENDMENT NO : 01 AMENDMENT DATE: 25.03.2008
AMENDMENT SHEET Sl no
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Introduction 25.03.08
‘Accuracy’ word deleted
Reasons
Signature QM
Signature Director
In line with ISO/ IEC 17025:2005
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National Accreditation Board for Testing and Calibration Laboratories Doc. No: NABL 164 Issue No : 01
Guidelines for Inter-Laboratory Comparison for Calibration Laboratories where formal PT programmes are not available Issue Date : 28.04.2005 Last Amend No: 01 Amend Date: 25.03.2008 Page No: i
CONTENTS Sl
Title
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Introduction
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2.
Procedure
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3.
Reporting Format
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National Accreditation Board for Testing and Calibration Laboratories Doc. No: NABL 164 Issue No : 01
Guidelines for Inter-Laboratory Comparison for Calibration Laboratories where formal PT programmes are not available Issue Date : 28.04.2005 Amend No: 00 Amend Date: -Page No: ii
Guidelines for Inter-Laboratory Comparison for Calibration Laboratories where formal PT programmes are not available Introduction: Calibration laboratories are generally working to different levels of Best Measurement Capability (BMC). Consequently, their performance is not judged by comparing their results with those of the other laboratories. Instead, their results are compared only to the Reference Laboratory’s results. Their ability to achieve the BMC for which they are accredited is evaluated by calculating the Error normalized (En) ratio.
Procedure: 1. The participating laboratory must prepare and communicate to NABL a program outline containing details of the artifact, parameters to be calibrated and reference laboratory selected in the reporting format-A. The laboratory shall select the calibration points in a manner to cover the entire range of the parameter selected. 2. The participating laboratory has to select a reference laboratory which should be either NPL or another accredited laboratory having better capabilities (smaller uncertainties/ better BMC) than the participating laboratory in that particular parameter. 3. The artifacts used in these programs should have sufficient resolution, repeatability and stability to allow the laboratory to report an uncertainty equal to their BMC as defined in their scope of accreditation/ application. 4. The participating laboratory has to communicate the calibration results to NABL before dispatching the artifact to Reference Laboratory in the reporting format - A. 5. After NABL approves the plan for program, participating laboratory should get the artifact calibrated from reference laboratory and analyze the results and calculate En ratio the as per the following:
National Accreditation Board for Testing and Calibration Laboratories Doc. No: NABL 164 Issue No : 01
Guidelines for Inter-Laboratory Comparison for Calibration Laboratories where formal PT programmes are not available Issue Date : 28.04.2005 Amend No: 01 Amend Date: 25.03.2008 Page No: 1/ 3
En =
LAB – REF √U2LAB + U2REF
Where, LAB is the participating laboratory’s result REF is the Reference Laboratory’s result ULAB is the participating laboratory’s reported uncertainty UREF is the Reference Laboratory’s reported uncertainty |En| ≤1 indicates the satisfactory performance of the laboratory |En|>1 indicates the unsatisfactory performance of the laboratory
National Accreditation Board for Testing and Calibration Laboratories Doc. No: NABL 164 Issue No : 01
Guidelines for Inter-Laboratory Comparison for Calibration Laboratories where formal PT programmes are not available Issue Date : 28.04.2005 Last Amend No: 00 Amend Date: -Page No: 2/ 3
Reporting Format - A Details of artifact (name, least count and range etc.): Parameter(s) selected for calibration:
Result
Participating laboratory (Name & address) Uncertainty BMC claimed reported
Reference laboratory (Name & address) BMC claimed
Signature Date:
Comments of NABL: Proceed further: Yes/No (if yes, please send the following details)
(Signature of NABL official) Date: Reference laboratory (Name & address) Result Uncertainty reported
Performance evaluation: Parameter(s)
En ratio
National Accreditation Board for Testing and Calibration Laboratories Doc. No: NABL 164 Issue No : 01
Guidelines for Inter-Laboratory Comparison for Calibration Laboratories where formal PT programmes are not available Issue Date : 28.04.2005 Last Amend No: 00 Amend Date: -Page No: 3/ 3
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