Noise Analysis of Photoelectric and Capacitive Detection of MEMS Accelerometer Signal

The thermo-mechanical noise and electrical noise of MEMS torsional pendulum accelerometer are analyzed respectively,in which the sensitive signal is detected by capacitive or photoelectric circuits.The thermo-mechanical noise of the MEMS sensing structure is 2.4 μgn/Hz, 0.28 μgn/Hz when the quality factor Q of the sensing structure equals 1,85,respectively.The electrical noise is 3.27 μgn/Hz for capacitive detection,while the photoelectric detection has a resolution of 0.05 μgn considering the electrical noise only.So the total noise of MEMS accelerometer with photoelectric detection is smaller than the total noise with capacitive detection.