Improvements in or relating to instruments for and methods of airborne measuring of derivatives of the vertical component of the earth's gravity field

摘要

846,201. Electric gravimeters. BOITNOTT, B. D. Oct. 1, 1958 [Oct. 1, 1957], No. 31405/58. Class 40 (1). Apparatus for determining the vertical rate of change of the earth's gravity field comprises an evacuated double chamber 1, 2, maintained vertical gyroscopically or by free suspension, containing three horizontal electrodes 9, 10, 11 and a cloud of mercury particles produced by applying a voltage to electrodes 5, 6 in the base of the chamber, the mercury vapour being ionized by radio-active material 22 located centrally outside the chamber, whereby, when the mercury particles are allowed to fall under gravity, the difference in the charge imparted to electrodes 11, 10 in unit time is indicative of the difference in the value of g. A cylindrical screening electrode 19 prevents the falling mercury particles from spreading out. Auxiliary electrodes 15, 16 at the top and bottom of the chamber may be momentarily supplied with a P.D. which will cause the mercury vapour to rise, so that the measurements can be repeated. The supply and measuring leads are interconnected via timing devices, and the whole apparatus may be airborne.