An Investigation into the Calibration of Gravity meters

Summary Gravity observations made with gravity meters over large gravity ranges have shown the instruments to be less satisfactory than is desirable. Figures are given showing the errors which have been found using three gravity meters under various field procedures and some possible causes of error are discussed. The scale constants of the gravity meters are shown to change substantially with time, and a system is described which was built into one gravity meter in order to check the scale constant at any time. The results obtained from this device are tabulated and discussed; no satisfactory mechanism has been produced to explain the change in scale-constant, and the calibration device has some use, although not so much as had been hoped. It is concluded that for the accurate measurement of large gravity differences careful operation of the gravity meters is essential, the calibration of the instrument being checked regularly; and that pendulum measurements may be preferable for the measurement of very large gravity differences.