Signal conditioning techniques for health monitoring devices

This paper presents aspects about biosignal data acquisition, applied in design of the medical measuring and recording devices. We are working on a mobile health monitoring project and the signal conditioning section will be used for ECG and EOG analog input signal recordings. This block of medical devices represents intermediate section between electrodes and analog to digital converters. The main goal is to view and measure clear waveforms of small level signals, so the quality and performance of the signal conditioning section is very important. We have made research about instrumentation amplifiers, filtering methods and operational amplifiers in order to obtain clear signals at desired voltage level. Data acquisition is made by Atmega 2560 microcontroller with 8 channel 10 bit ADC. For experimental purposes we have designed and built the signal conditioning board with adjustable gain for both: the instrumental amplifier and the power amplifier. Three filtering methods were evaluated regarding to the implementing costs, quality and power consumption, and two of them were built and tested. The first is operational amplifier based analog active filter, the second is elliptic, switched capacitor filter in one chip, and the third filter is embedded in a multifunction analog front end with software control. The signal conditioning board was tested and evaluated using the ECG input signal. After testing the filters and comparing the results, we consider that medical oriented low power analog front ends and signal processors are the best solutions to design quality wearable health monitoring and recording devices.