A weak capacity measurement system with vector ratio method based on phase sensitive detection

Abstract

The paper presents a weak capacity measurement method with vector ratio based on phase sensitive detection (PSD). This method can separate the real weak signal from noise with high SNR (Signal Noise Ratio). In practical circuit achievement, the weak signal should get through a pre-process channel for filtering and amplifying before it is put into PSD. In order to eliminate DC offset voltage and current, a dynamic adjustment circuit for reducing the operator's offset is designed in the pro-process channel. The advantages and effectiveness of this method and circuit are verified by experimental testing.