Low cost calibration free Pulse oximeter

This paper deals with a pulse oximeter device, which measures pulse rate and blood oxygen levels of a person in a non-invasive way without any need of calibration. Current models involve calibration and a complex analog circuitry. The device proposed is novel not only in terms of computing the oxygen saturation levels without any calibration but also uses the digital computation power of the microcontroller leading to a simpler circuit design. Two Photo-plethysmographic (PPG) signals corresponding to Red and Infrared wavelengths are obtained from the sensor by using an Arduino microcontroller and subsequently signal is transferred to PC via serial communication where all the signal processing is carried out using MATLAB. Oxygen levels in blood are then determined using Beer Lambert Law while the Pulse rate is calculated both in time and frequency domain. Thereafter results obtained are compared with a commercial pulse oximeter. Accuracy of ±5% for oxygen saturation levels and ±7% in case of pulse rate values is achieved. This design removes the need for calibration and aids in reducing the cost of the pulse oximeter to less than $20 which can be used in the future for practical and research purposes.