| 摘要 |
An improved gravimeter mechanism includes a mass balanced cam having mutually opposed camming surfaces for controlling the free fall of a measuring mass. The cam is attached to a camshaft which turns at a constant rate, the rate being selected so that the drop time appropriate to achieve lift-off of the dropped object together with the time required to return to the start position equals the cam's rotational period. The mutually opposed camming surfaces cooperate to drive both a cart which supports a measuring mass and a compensating mass which is built into the gravimeter mechanism. The cam drives the cart, the measuring mass, and the compensating mass so that the time varying reduction in weight produced when the measuring mass is in free fall is exactly compensated by the compensating mass which is driven by the opposing camming surface. The opposing camming surface is displaced from the lift off region of the camming surface which drives the cart and measuring mass by 180 degrees. The measuring mass contains a mirror element of a Michelson interferometer, and the interferometer produces a signal indicative of the rate of free fall, which is directly proportional to the local gravity.
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