RESUMO
Objective To research a pure capacitance sensor for acquisition of cardiac phonocardiogram. Methods Under the phantom power supply (48V), the faint vibration signal of the heart was processed into electric signal by larger pre - treatment circuit module, shielded cable and the sensor pre-amplifier of circuit module. Results With some experiments, it can be proved that the sensor won't have affect on the sound field which frequency band under 1 000Hz and can detect the level of sound field like 20dB:30dB and 150dB or higher. Conclusion So with the sensor, the precise signal which can exactly reflect the status of patients' hearts can be detected, and it suits to work in complex condition for its high sensitivity, wide frequency band and low distortion.