Modular design of a long-term portable recorder for physiological signals

A portable biomedical signal recorder is valuable for the detection of acute symptoms. By the use of an ambulatory recorder, investigators and clinicians have more opportunity to analyze paroxysmal or sudden symptoms from the long-duration recorded signals. We propose a modular recorder that contains a motherboard, modules, and an isolated RS-232 interface. The modules have been modified to measure electrogastrogram (EGG), electrocardiogram (ECG), and electroencephalogram (EEG) signals. The compact motherboard includes a microcontroller with a built-in A/D converter, secure digital (SD) memory card, and the driven-right-leg (DRL) circuit. The power consumption of the proposed recorder is less than 2 mA (6 mW). It can continuously record a lead-II ECG signal with a 10-bit resolution for 3.9 days. As a result, the design is suitable for the purpose of long-term portable recording.