Radiation response of a MEMS accelerometer: an electrostatic force

Particle irradiation on the mechanical sensor of the ADXL50 microelectromechanical accelerometer shifts the output voltage. An earlier conclusion, that a dielectric below the sensor becomes charged, is extended by quantifying the effect of this charge on device output. It is shown that an electrostatic force is consistent with the observation that the output voltage shift is independent of acceleration. Possible charging mechanisms are suggested. An appendix derives a convenient algorithm for calculating electrostatic forces, which may also be used for other MEMS devices.