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CoverNewton's Bulletin


Issue n. 3, January 2006   [pp. 5-8]



Calibration of a 3-accelerometer inertial gravimetry system for moving gravimetry


B. de Saint-Jean, J. Verdun, H. Duquenne, J.P. Barriot, J. Cali

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Abstract

A moving inertial gravimetric system is being developed, consisting of three high precision accelerometers measuring accelerations along three non parallel axes. The signal delivered by each accelerometer is an electric current, the intensityof which is proportional to the acceleration experienced by the test mass of the accelerometric sensor. This 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 at 31.25 Hz, that is one sample every 32 ms, while the temperature is sampled at a rate of one sample every 4.096 s. Our aim is to carry out the calibration of this system in order to derive the relationship between each digitalized value given by the accelerometers and the actual acceleration, taking into account temperature variations. Our calibration system permits to tilt simultaneously the three accelerometers above a point where gravity has been precisely determined. Thus, the accelerometers can sense any acceleration value between 0 and the value of gravity at the measuring point (accelerometer axis is then vertical). We discuss the results of the calibration by looking at the residuals between observed values and those coming from different theoretical calibration functions. We particularly focus on the perturbing phenomena such as temperature or misalignment of the sensitive axis.