Inertial rotation sensors are known that comprise a vibrating bell, generally a hemispherical bell, having its surface metallized to receive a bias voltage, the bell having an edge facing electrodes that are carried by a stand. The electrodes are subdivided into control electrodes and detection electrodes. Control signals are applied to the control electrodes so as to cause the vibrating bell to vibrate, thereby deforming the bell with deformations of orientation that is sensitive to rotation of the sensor. The detection electrodes serve to measure the orientation of bell deformations and, by suitable processing, to deduce therefrom the rotary movements of the sensor. The displacements of the resonator relative to the electrode-carrier stand at two ends of a diameter are equal in modulus and in sign when they result from control signals for sustaining vibration, and they are equal in modulus but opposite in sign when they result from parasitic displacements of the bell, in particular bending of the axis of the bell. Summing the measurements taken on a given diameter serves to eliminate the parasitic displacements providing the detection gains are equal.
It is also known that the gain for each electrode is a function firstly of the area of the electrode and secondly of the size of the airgap between the electrode and the facing edge of the vibrating bell. In spite of very strict manufacturing tolerances, different electrodes have different areas or different airgaps leading to differences in gain between the electrodes, and this applies regardless of whether the electrodes are control electrodes or detection electrodes. In addition, in existing systems, each electrode is connected to a processing system and the various processing systems may also present gain differences between one another. As a result, in general, anisotropy exists both for control and for detection. This anisotropy is a source of error when calculating the rotary movements of the sensor.