Medical Oxygen Sensor Based on Acoustic Resonance Frequency Tracking Using FPGA

The aim of this study is to develop a noninvasive medical oxygen sensor using the acoustic resonance frequency tracking technique. To make it realize, the optimization of sound-resonance cavity based on an acoustic longitudinal mode is used as the sensing element for this sensor. A new method for resonance frequency tracking is presented by the phase difference comparison and calculation. Based on the relationships among the excitation and response signals of the sound-resonance cavity, the phase difference comparison and calculation algorithm had been used to automatically track the resonance frequency. The resonance frequency tracking is implemented by the field-programmable gate array (FPGA) device. The performance of the sensor is demonstrated by measuring the concentration of oxygen. The test results show that a sensitivity limit of 1000 ppm, a response time of 4 s, and detection capabilities over a broad concentration range from 1000 ppm to 100% have been demonstrated at one atmosphere. Results demonstrate that this work is expected to provide a new technical means for medical oxygen monitoring.