Dry electrode sizes in recording ECG and heart rate in wearable applications

The rise of wearable electronics is paving the way for textile integrated sensor applications. ECG and heart rate monitoring are common in health care and consumer applications, respectively. In short term monitoring Ag/AgCl, conductive polymer or fabric electrodes can be used. In long term monitoring the electrolyte and adhesives may cause skin irritation, therefore textile integrated skin friendly dry electrodes may be a solution. The electrodes need to be cost-effective, easy to integrate, need no special care from the user and perform well. Conductive polymer and textile used in sports applications perform poorly when used without electrolyte. Stainless steel is common, affordable, easy to process, biocompatible (selected alloys), and provides adequate ECG quality. In this paper, we study different size stainless steel dry electrodes in ECG and heart rate monitoring and compare those with commercial disposable Ag/AgCl electrodes. The results show that stainless steel dry electrodes performed well throughout the tested activities if the circular electrode diameter was 20 mm or larger.