Optimum Place for Measuring Pulse Oximeter Signal in Wireless Sensor-Belt or Wrist-Band

This study was done in order to solve the optimum place for integrated pulse oximeter in case of a belt around human chest or wrist so that it would provide reliable oxygen saturation (SpO₂) readings for noninvasive constant health monitoring in modern wireless applications. In the study four spots on the wrist and on the chest were chosen and measurements from these spots were done by using a special device with an adjustable angle between light detector and the light sources. Then resulted signals were analyzed by calculating the average amplitude, normalized amplitude and signal-to-noise -ratio (SNR). Considerably clear signals were achieved both from wrist and chest and best resulted SNR was 2 7 dB from the chest. The highest normalized signal amplitude was detected from the wrist appearing as big as 5.9% of the total measured signal, which was relatively high compared to other values. Results were promising and showed that an easy portable monitoring device is possible but also many problems, that should be overcome, were detected.