EMFi material as wearable heart rate sensor for night time recordings

We propose a method for night time monitoring of heart rate. Our method uses one or more pressure sensitive elements integrated into a wristwatch. The sensing elements are made of film type electret material called EMFi (Electro Mechanical Film). We designed the signal processing algorithms keeping in mind on-line processing and later integration into a micro controller for wearable applications. We have evaluated our method by comparing beat-to-beat heart rate values obtained with EMFi sensors with accurate reference values calculated from reference ECG signal. We suggest based on the 209 s average continuous recognition time and 0.51 bpm mean error that our method provides adequate accuracy for night time heart rate and heart rate variability analysis, which enables the method to be used in various applications.