A method to estimate the time-position coordinates of a free-falling test-mass in absolute gravimetry

As part of the research activity carried on at the Institute of Metrology 'G Colonnetti' IMGC-CNR in Turin on the development of the IMGC02 absolute gravimeter, a method to estimate the time occurrences of interference fringes was developed and tested. The capabilities of the IMGC02 have been enhanced by: increased flexibility in timing measurement, the possibility of real-time analysis and the removal of frequency-dependent time delays introduced by the timing electronics. A Monte Carlo simulation has shown, in the case of an ideal frequency and length reference, that the resolution of the waveform digitizer that samples the interference signal can limit the accuracy of the timing measurement. Nevertheless, the expected systematic bias in the absolute measurement of the acceleration due to gravity, g, introduced by this data processing technique is negligible when compared to the current instrument uncertainty.