<title>Investigations to assess the best accuracy attainable in accelerometer calibrations</title>

Abstract

National Metrology Institutes (NMIs) worldwide make use of laser interferometry in compliance with the new International Standard ISO 16063-1 1 : 1999 to realize and disseminate the unit and the associated scale of the physical quantity of acceleration. By convention, the dissemination has up to now been carried out by primary vibration calibration of reference standard accelerometers as are used in accredited calibration laboratories to calibrate working standards by comparison. The calibration and measurement capabilities (CMCs) of the NMIs are published in the BIPM Key Comparison Database, Appendix C (cf. http://www.bipm.org, 2001). Recently, special commercial laser vibrometers have been developed which comply with the ISO standard and, consequently, may be applied as reference standards at any level of the traceability chain provided they are traced back to appropriate national standards and are provided with adequate uncertainty budgets. Though it may be expected that all calibration laboratories (NMIs included) establish uncertainty budgets in compliance with the ISO Guide to the Expression of Uncertainty in Measurement (GUM), the accuracy attained can be reliably assessed only by appropriate comparison measurements. A general account is given of the state of the art in vibration measurements and transducer calibration using laser interferometry, focusing on comparison results which have confirmed the lowest measurement uncertainty achieved so far. Results of vibration measurements and calibrations obtained by different interferometric methods will be presented. An analysis of international and regional comparison measurements (accelerometer calibrations) will be reported on.