Thursday 25 August 2005

G6

PTH0064
Calibration of a 3-accelerometer inertial gravimetry system for moving gravimetry
de Saint-Jean, Bertrand¹, Verdun, Jerome¹, Duquenne, Henri¹, Cali, Jose²
1 LAREG/IGN, France
2 ESGT, France
Author email: desaintjean@ensg.ign.fr
A moving inertial gravimetry system is now being developed, consisting in 3 high precision accelerometers measuring accelerations along 3 non-parallel axes. The signal provided by each accelerometer is an electric current, the intensity of which is proportional to the acceleration experienced by the test mass of the accelerometer sensor. The sensor is also very sensitive to temperature variations which are continuously monitored by an internal temperature sensor. The current given by each accelerometer is transformed into a voltage sampled with a frequency at 32.25 Hz, while the temperature is sampled at a rate of one sample every 4.096 s. Our aim is to carry out calibration of the accelerometer system in order to derive the relationship between each digitized value given by the accelerometers and the actual acceleration, taking care of temperature variations. Our calibration system permits to tilt simultaneously the 3 accelerometers above a point where gravity has been precisely measured. Thus, the accelerometers can sense any acceleration value between 0 and the value of gravity at the measuring point. The slant of accelerometers can be precisely measured by means of self-collimation method (standard deviation: 2.27 arsec). We discuss results of the calibration experiment by looking at the residuals between observed values and those coming from different modelled calibration functions. We particularly focus on the pertubing phenomena such as temperature or misalignment of accelerometer sensitive axis.

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