ISO/IEC 17025 - Laboratory, ISO 17025 For Calibration Laboratory

Calibration laboratories are accredited after it is demonstrated that a laboratory complies with the requirements of international standard ISO/IEC 17025:2017. In view of generic nature of the standard the requirements stated there in, need to be further redefined in specific fields of calibration.

Best Measurement Capability (BMC) is one the parameters that is used by NABL to define the scope of an accredited calibration laboratory, the others being parameter/quantity measured, standard/master used, calibration method used and measurement range. The BMC is expressed as”the smallest uncertainty that a laboratory can achieve when calibrating a device that is effectively ideal”. It is an expanded uncertainty estimated at a confidence level of approximately 95% corresponding to a coverage factor k=2.

The laboratory’s ability to achieve their claimed BMC shall be evaluated based on its performance during the on-site assessment and by review of proficiency testing results, wherein the laboratory has participated.

The definition of BMC implies that within its accreditation a laboratory is not permitted to report a smaller uncertainty of measurement than the BMC endorsed on its scope of accreditation. This means that the laboratory shall be required to state an uncertainty not better than that corresponding to the BMC whenever it is established that the actual calibration process adds significantly to the uncertainty of measurement. The BMC is applicable only to the results for which the laboratory claims its status as accredited laboratory. It is therefore a realistic means for customers to select and compare accredited laboratories’ capabilities. The scope of accreditation of calibration laboratory shall be identified as source and measure. Source define the sourcing capability of a laboratory where as measure define the measuring capability of a laboratory.

All the parameters for which accreditation is sought must be expressed in S.I. Units, wherever applicable.

Accreditation of a calibration laboratory will require assessment in respect of organization, staff, equipment and traceability of its calibration, laboratory accommodation and environmental conditions, safety, handling of calibrated equipment and equipment under calibration, measurement capability and recording system, etc., as per ISO/ IEC 17025: 2005 General Requirements for the Competence of Testing and Calibration Laboratories.