Acoustics 08 Paris 2217 The paper reviews the background of the primary calibration of acoustic emission sensors and the determination of uncertainty by this calibration. There are discussed the aims and the purpose of the primary calibration and main sources of uncertainty in practical usage of calibration results. The comparison of the results of three methods is presented. The shape of calibration characteristics corresponds well up to 300 kHz. The calculations of the uncertainty of those

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... hods are closely described. UT 1000 (PAC) was used as the reference sensor. The problem of propagation of uncertainty in the FFT was solved. Uncertainties of measurements by primary calibrations are determined and presented in the paper. The influence to the uncertainty of main sources was described and is presented. The big influence on uncertainty in reciprocity calibration was the influence of remounting reference sensor and pair sensors. Acoustics 08 Paris