An unobtrusive measurement system for night-time heart rate (HR) monitoring is presented. The system uses capacitive electrodes that do not require galvanic skin contact, thus allowing user to wear clothes while being monitored. The electrodes are located transversely on the bed and the electrocardiographic signals are measured between each electrode and a common reference. The signals are then combined in order to remove the common mode move-ment artifacts and the best one is selected for HR detection.
The average RR-interval detection coverage with five test subjects in one hour long measurements was 81.0 %. The average mean absolute error compared to the reference ECG signal was 1.78 ms in average.