Portable ECG Data Acquisition Circuit And The Underlying Driver Development

As the improvement of people’s living standards, cardiovascular disease to become first major threats to people’s health. ECG is the important basis for clinical diagnosis of heart disease, electrocardiogram monitor made of principle ECG has functions of collecting and analysis of ECG. Although general electrocardiogram monitor can comprehensively monitor and analyze various parameters of patient, now is only common in major medical institutions like hospitals because the price; General household portable electrocardiogram monitor can monitor acquisition and record ECG, but has nor detection or analysis capabilities, can’t easily rapidly give a visual test result. For the ARM platform as the current smart phone platform, we’re working on a portable electrocardiogram monitor system based on ARM9, this paper introduces the data acquisition circuit and the underlying drivers of design work.In term of hardware designing, with the ECG features of small amplitude, low frequency, big interference and many differences, I choose high precision operational amplifier OPA2277and switched capacitor filter MAX295as the core to design the amplifier and filter circuits of-electrocardiogram monitor. In the ECG acquisition process, I use standard ECG leads system to collect ECG at the fix positions, through the silver chloride electrode. I design preamplifier for minimum20times to preliminary zoom ECG signal, and eliminate the high common-mode signal. At the same time, I set main amplifier for maximum50times to meet the requirement on signal of the system. Through magnification of preamplifier and main amplifier the ECG signal is zoomed from micro voltage level to voltage level at1000times to fit the analog to digital conversion process. In trend to filter the interference signal, such as ECG baseline drift, electrode interference, electromyographic interference, and get the pure ECG signal, I use the switch capacitor filter MAX295and KRC low pass filter to analog filter after the main amplifier; Finally it is sent into the ARM platform Convert to digitized ECG signal by a10-bit A/D converter chip. In term of software designing, I develop a series of underlying drivers on WinCE platform for peripherals of the ECG systems. Depending on the configuration, the system requires the I/O driver, A/D driver, LCD driver and etc. After written the driver, it needs to be compiled to DLL files, and then can test its functionality on the burn-in system is perfect, or test its loading speed, corresponding speed and completeness with the CETK.In the test, we use acquisition circuit to do couples of tests on human ECG signal in separate times, to test SNR ratio, magnification and other features. The results show that the ECG acquisition circuit can filter out interference and zoom ECG signal as the requirement of system.