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Flotation as a Technique for Testing Low-Level Accelerometers in the Earth's Gravitational Field.
STANFORD UNIV CA DEPT OF AERONAUTICS AND ASTRONAUTICS
Laboratory calibration of accelerometers which operate in the range from ten to the minus three g to the ten to the minus eight g or lower has previously been limited by the earths gravitational field to uncertainties on the order of ten to the minus six g. A new technique that reduces these limitations by several orders of magnitude is presented. The accelerometer proof mass is immersed in a flotation fluid which supports all but an accurately controlled small fraction of its weight. Test inputs and the instrument support forces are thereby maintained precisely at orbital levels. Seismic noise, similarly attenuated, becomes insignificant. Choosing sulfur hexafluoride SF6, a heavy gas, for the flotation fluid, permits a wide range of density levels which can be servo-controlled volumetrically, and minimizes the interaction effects of the flotation fluid and the accelerometer. Limitations on the types of instruments that can be tested by this technique are discussed. Author