Drift of MEMS Closed-Loop Accelerometers Induced by Dielectric Charging

In this work, the drifts of the bias and scale factor induced by the dielectric charging are studied for micro-electro-mechanical system (MEMS) closed-loop accelerometers. At first, the equations of the feedback electrostatic forces, including the built-in voltages resulted from the dielectric charging, are built up for the two capacitors of the accelerometers. Then, the models for the drifts of the bias and scale factor both are established. Based on the models and experimental data, it is found that the drift of the scale factor is always negative because the built-in voltages always decrease the scale factor. However, the drift of the bias can be negative or positive because it is in proportion to the built-in voltages' difference of the two capacitors, which may be negative or positive. The major output error for the small input acceleration is caused by the drift of the bias. However, for the large acceleration, the error induced by the drift of the scale factor is also vital. Finally, the method of choosing the frequency of the ac reference voltage for suppressing the dielectric charging based on the drift of the scale factor is established. The feasibility is verified by the experimental data.