期刊
IEEE SENSORS JOURNAL
卷 21, 期 4, 页码 5340-5348出版社
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JSEN.2020.3031066
关键词
Microphones; Electron tubes; Pressure sensors; Pressure measurement; Thermal sensors; Signal to noise ratio; Time measurement; Biosignal sensing; pneumatic method; ballistocardiograph; thermal gas flow sensor; differential pressure sensor; bed sensing; non-invasive sensing
The study introduces a non-invasive biosensing method utilizing a differential pressure sensor to measure pressure on a tube under a bed cushion. Compared to methods using microphones, this approach offers better dynamic range and signal-to-noise ratio. Experimental results show that the proposed method based on the differential pressure sensor provides higher signal-to-noise ratio when measuring heart beat signals.
We propose a non-invasive pneumatic biosensing method that measures the pressure on a tube placed under a bed cushion. Although similar methods use microphones for pressure sensing, the high sensitivity of microphones may cause problems such as saturation, slow recovery from saturation, narrow dynamic range, and low signal-to-noise (S/N) ratio. However, the proposed method uses a differential pressure sensor based on the thermal flow principle which has been developed and commercialized recently. We derive theoretical models of both microphone and thermal flow measurements to show that the proposed method can solve the problems of methods based on microphones. Basic experimental results validate both models providing the time constant (65 s), saturation range (-80-+40 Pa), noise level (4.02 Pa), dynamic range (32 dB) and S/N ratio (21 dB) of the low-frequency microphone developed for biosignal measurement and the superior time constant (0.012 s), saturation range (-500-+500 Pa), noise level (0.82 Pa), dynamic range (62 dB) and S/N ratio (56 dB) of the proposed method based on a differential pressure sensor. Furthermore, the effective S/N ratio in the measurement of heart beat signal was also compared between the low-frequency microphone and the proposed method. The former showed S/N ratio (22.1 dB), and the latter showed S/N ratio (28.1dB).
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