This application discloses a precision
capacitance sensing system, comprising a modulation
signal source, a sensitive probe, a differential
transformer bridge, a
signal amplification link, an
analog multiplier, and a low-pass filter circuit, all connected in sequence. It also includes a
demodulation reference
signal source, the output of which is connected to the second input of the
analog multiplier. The
demodulation reference
signal source is used to generate a multi-frequency combination
demodulation reference signal, which is composed of a
fundamental frequency component and at least two
harmonic components superimposed. This invention also discloses a precision
capacitance sensing method. By employing a specially designed demodulation reference signal, this application ensures that the
system output remains constant within a continuously varying range of the demodulation
phase difference, thereby achieving complete insensitivity to
phase difference fluctuations and effectively overcoming the performance
bottleneck that has long constrained high-precision
capacitance sensing.