| The objective of this thesis is to present the designing of the ring sensor to monitor a patient 24 hours a day for a telenursing system. In order to monitor beat-to-beat pulsation, the ring sensor is attached to a finger base, and an RF transmitter is used to send the data to the host computer. Here the two major design issues minimizing the motion artifact and minimizing the battery power consumption are discussed. In order to reduce the effect of acceleration, external force, and ambient light, and also to hold the sensor securely and gently on the skin so that at the finger the circulation is not obstructed, an efficient double ring design was developed previously and is evaluated in this thesis. For understanding the mechanism of motion artifact by external forces, a mathematical model that describes the finger photoplethysmography was adapted. In relation to the characteristics of the individual components, sampling rate, and CPU clock speed the total power consumption of the ring sensor circuit is analyzed. For minimizing the power consumption, the desirable optical conditions could be thus obtained. Based on the artifact-resistive attachment method and power budget analysis a prototype ring sensor design has been verified. Although no experiments were carried out in this thesis study, the requirements of the ring sensor such as compactness, minimum loading effects, motion artifact reduction, and low battery power consumption are all studied. Finally, based on the analysis and in literature results the guidelines for designing the ring sensor are presented. |
