Wearables and the Quantified Self: Systematic Benchmarking of Physiological Sensors.

Günther Sagl,Andreas Petutschnig,Bernd Resch,Kalliopi Kyriakou,Frank H Wilhelm,Michael Liedlgruber

doi:10.3390/s19204448

Abstract

Wearable sensors are increasingly used in research, as well as for personal and private purposes. A variety of scientific studies are based on physiological measurements from such rather low-cost wearables. That said, how accurate are such measurements compared to measurements from well-calibrated, high-quality laboratory equipment used in psychological and medical research? The answer to this question, undoubtedly impacts the reliability of a study’s results. In this paper, we demonstrate an approach to quantify the accuracy of low-cost wearables in comparison to high-quality laboratory sensors. We therefore developed a benchmark framework for physiological sensors that covers the entire workflow from sensor data acquisition to the computation and interpretation of diverse correlation and similarity metrics. We evaluated this framework based on a study with 18 participants. Each participant was equipped with one high-quality laboratory sensor and two wearables. These three sensors simultaneously measured the physiological parameters such as heart rate and galvanic skin response, while the participant was cycling on an ergometer following a predefined routine. The results of our benchmarking show that cardiovascular parameters (heart rate, inter-beat interval, heart rate variability) yield very high correlations and similarities. Measurement of galvanic skin response, which is a more delicate undertaking, resulted in lower, but still reasonable correlations and similarities. We conclude that the benchmarked wearables provide physiological measurements such as heart rate and inter-beat interval with an accuracy close to that of the professional high-end sensor, but the accuracy varies more for other parameters, such as galvanic skin response.

Highlights

In the last decade, the body of literature about physiological sensing and deriving emotions from physiological parameters has grown significantly
The body of literature about physiological sensing and deriving emotions from physiological parameters has grown significantly. One reason for this is the rapid increase in variety of affordable wearable sensors that measure a broad range of physiological parameters such as heart rate, galvanic skin response, skin temperature, and others
Understanding a sensor’s quality and accuracy is critical because the research results may otherwise be unreliable: while traditional professional wired sensor devices, which have been used for some time in laboratory and ambulatory studies in the fields of psychological and medical research, are proven to be highly accurate, most wearable sensors used in previous studies are not

Summary

Introduction

The body of literature about physiological sensing and deriving emotions from physiological parameters has grown significantly One reason for this is the rapid increase in variety of affordable wearable sensors that measure a broad range of physiological parameters such as heart rate, galvanic skin response, skin temperature, and others. Community that promotes the idea of 24/7 tracking and monitoring has been growing significantly [1,2,3] These new low-cost wearables are increasingly used in scientific studies in a variety of areas like health research, well-being assessment, disaster management, emotion information extraction and spatial emotion analysis, and stress detection [4,5,6,7,8,9,10,11,12,13]. Some wearable sensors have been released that are certified and comply with a number of international standards (sensor technology, wireless communication, data transmission, etc.), which makes them a viable alternative to traditional wired equipment

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