Calibration Capability Analysis for Digital Pressure Gauge through Measurement Audits: The Alternative to Proficiency Testing

Under ISO/IEC 17025, the laboratories are generally required to participate in interlaboratory comparisons or proficiency testing to maintain their high competence and assure the quality of results for establishing the effectiveness and comparability of calibrations. Participation in proficiency testing to assure the good performance and capabilities is the basic requirement for laboratories in Taiwan to apply for accreditation certification or seek an extension of the certification issued by Taiwan Accreditation Foundation (TAF), the main accreditation body in Taiwan. When the proficiency testing is not available, the calibration laboratories in Taiwan shall participate in the measurement audits under the requirement of TAF. The Center for Measurement Standards of Industrial Technology Research Institute (CMS/ITRI) not only organize the proficiency testing programs regularly but also provide the measurement audits to meet the needs of the calibration laboratories that apply for the new accreditation items. In the last two years, the tests of energy efficiency of compressed air systems were required by law, digital pressure gauge calibration services are urgently demanded in industry. In order to expand their measurement scopes to include the digital pressure gauge calibration, 11 laboratories applied for measurement audits with the CMS/ITRI since there was no proficiency testing program for digital pressure gauge calibration. In these audits, the National Measurement Laboratory (NML) provided the reference values for the digital pressure gauges. In this paper, the results of interlaboratory comparisons for 11 laboratories were analyzed based on the outcomes of the measurement audits. Through the statistical analysis, the comparison results showed reasonable agreements in general among the measurements on digital pressure gauge calibration for most of calibration laboratories. It can also be found in this analysis that the measurement audits can be used in confirming the competence of the laboratories and provide solid proof for accreditation purpose.