Amplitude stability analysis and experimental investigation of an AC

excitation signal for capacitive sensors

Ke Li, Yanzheng Bai*, Ming Hu, Shaobo Qu,

Chengrui Wang, Zebing Zhou*

Low-noise capacitive sensor is widely used in electrostatic accelerometers and inertial sensors. An AC excitation signal is necessary to realize the amplitude modulation of the slow differential capacitance. But the amplitude stability of this AC excitation signal will directly influence low-frequency performance and dynamic range of capacitive sensors which results in the deviation of scientific requirements. In this paper, a stable AC excitation signal is realized based on the classical direct digital frequency synthesis technology. The mathematical model of amplitude stability is systematically set up, and there are four main influencing factors including transition time stability of the digital-to-analog converter (DAC), frequency stability of the crystal oscillator, voltage stability of the reference and gain stability of the band-pass filter (BPF). Each contribution of these four sources is theoretically analyzed. Finally, an evaluation prototype board is achieved to investigate the stability experimentally. Performance testing results show that the amplitude stability could reach approximately 16 ppm/Hz1/2at 1 mHz under present optimal components selection, and transition stability of the DAC is the primary factor for further improvement.

期刊名：Sensors and Actuators A: Physical

期/卷：309 (2020) 112020

页码：1-6

发表时间：2020年7月

DOI: 10.1016/j.sna.2020.112020