The Acoustics Section of NPLI maintains two primary standards, viz. the standard of sound pressureand of acceleration amplitude. The primary standard of acceleration amplitude is maintained through absolute calibration of standard accelerometer as per ISO 16063-11:1999 by laser interferometric technique using the sine - approximation method in the frequency range 5 to 5000 Hz with an overall expanded uncertainty of +-1.0percent. The accuracy of primary standards is verified periodically through participation in key-comparison exercises with leading National Measurement Institutes (NMIs) in the world. The accuracy of transfer standards such as vibration level calibrator (+-1.5percent) is determined with the help of transducers calibrated by absolute methods. The working standard/measurement accelerometers are calibrated with the help of transfer standards with an overall expanded uncertainty of +-1.5percent. The paper describes the salient features of the accelerometer calibration carried out at NPLI along with an estimate of the associated uncertainty in calibration.
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