Abstract
A surface ship gravity meter has been newly designed and manufactured by using a servo accelerometer as the gravity sensor, aiming at mechanical toughness and immunity from the ship's environments. This meter is characterized by its sensor, in which a proof mass is supported electromagnetically in order to balance the gravitational force. The platform where the gravity sensor is placed is kept horizontal by being remotely controlled by a vertical gyroscope installed beside. A servo accelerometer is usually so rugged that it can withstand the acceleration as large as ±10G. This device, however, is of the type analogue device, and so it has been thought difficult to attain a high accuracy level . The gravity sensor used for this gravity meter has been manufactured by solving most of the difficulties in virtue of selection of materials, high stabilization of electric voltage and efficient temuerature control. Tests both on land and sea showed that the gravity meter is accurate to 0.1-0.5 mgal order. This gravity meter has been manufactured originally for the purpose of installing on board the Ice Breaker “FUJI” that is used for the Japanese Expedition of the Antarctica. The name “NIPRORI” is taken after a combination of the abbreviations of the National Institute of Polar Research (NIPR) and the Ocean Research Institute (ORI) of the University of Tokyo.
