Wearable impedance plethysmography and electrocardiography sensor

Wearable technology has become increasingly popular in the last few years. This project describes the design and implementation of a wearable impedance plethysmography and electrocardiography sensor. This sensor is developed to be compact and lightweight while having a very extended battery life. This way, it can be easily integrated into other wearable devices or into clothing or shoes. The acquired IPG and ECG data will be transmitted in real-time to a receiving host for further storage and processing by using the Bluetooth Low Energy protocol. By using a so widespread low energy wireless protocol, the data can be received into any compatible device, such as smartphones, laptops or even specialized systems. An android application showing a real-time graphic of the measured signals is also developed for demonstration purposes. To meet the low power consumption requirements of the analog front-end circuitry, multiple techniques were used, such as using low power versions of components such as operational amplifiers and even taking advantage of their limitations to improve circuit performance characteristics. Other techniques such as sensing the correct placement of electrodes or disabling parts of the circuitry when not needed or the signal is not available were also used. A current consumption for the analog frontend in the order of only 100 µA to 200 µA at 3V was achieved while continuously providing both IPG and ECG data. For the digital circuitry, consisting mainly of the nRF51822 System on Chip from Nordic Semiconductor and some peripherals, multiple techniques of power consumption minimization were also used. A current consumption of around 200 µA to 300 µA was achieved, again at 3V, during continuous data processing and transmission. A prototype was implemented on a PCB. Unfortunately, full functionality was not achieved mainly due to some hardware failures and time constraints, however, as multiple innovative solutions were implemented, this work will provide useful information to improve other research projects in this area.Objectius de Desenvolupament Sostenible::3 - Salut i Benesta