Development of a portable multi-functional patient monitor

This project aims to develop a microcontroller-based portable multi-functional patient monitor. The monitor is designed to record four channels of biosignals simultaneously: 2 channels of electrocardiogram (ECG), body temperature and non-invasive blood oxygen level (SpO₂). The monitor consists of 3 functional parts: biosignal conditioning, digital circuit and storage, on board and host software. The biosignal conditioning part consists of four analogue circuit modules, one for each channel of biosignal. In general, each analogue circuit module carries out differential amplification, band-pass filtering, power line interference elimination, dc level restoration, and output amplification. The digital circuit and storage part consists of a 89C52 microcontroller, an 8-channel A/D converter, an LCD panel and an SRAM data store. To overcome the limited memory addressing space of the microcontroller, the SRAM data store is configured and managed under the bank switching technique. In this project, 8 × 32Kbytes 62256 SRAM chips are used. On board program is written in assembly language and pre-installed in the internal ROM of the microcontroller. The host PC software is written in Java. Recorded biosignals can be transmitted to the host PC via a serial link for display, analysis and permanent storage. At present, the ECG and SpO₂ modules are completed. Testing has been carried out to record these two biosignals simultaneously. On-going work is in the development of body temperature module and the expansion of data store.