Some pressure test phenomena of worden and CG-2 (sharpe) gravimeters

Summary

The results of pressure tests of gravimeters Worden No. 961, CG-2 Nos 174 G, 323 and 374 in a pressure chamber are presented. Apart from deriving the barometric correction, the authors have also studied accompanying phenomena, which occur during pressure tests of gravimeters — the barometric “after-effect” and hysteresis. The processing of the results in two ways differing in the method of eliminating the drift of the gravimeter, yields nearly identical results. The hysteresis was investigated for atmospheric pressures of 720±150 Torr (1 Torr=0.133322 kPa), a rate of change of 30 Torr/min and a temperature of 22°C. The barometric after-effect was investigated in greater detail for the CG-2 gravimeter No. 174 G at a pressure difference of 225 Torr, rate of change of 30, 15 and 7.5 Torr/min and a gravimeter heating temperature of 35 °C. It was also found that the barometric correction can be determined, using the method given, with sufficient accuracy. As a result of the existence of hysteresis, however, the derived results must be applied carefully in field gravity measurements with some gravimeters.