The Research And Design Of Wireless ECG Monitoring And Warning Device

Based on the design requirements, we studied wireless ECG monitor equipments and designed ECG signal sampling module, central control module, PTR2000 wireless data transfer module.In order to sample the weak ECG signal under the noisy background, amplifying circuit and noise suppression filtering circuit are designed in the ECG signal sampling module. Human's ECG signals are weak bioelectrical signals with high inside resistance in signal source. Hence, to accurately measure ECG signals, the design core is ECG signal prefix processing circuit. Buffer circuit is the necessary circuit to transform resistance and to change the ECG signals with high inside resistance to electrical signals with low inside resistance. Signal amplifier's main performance features include high gain, high input resistance and high CMRR. To keep signals in a stable status, input offset voltage and small bias current are also required; the amplifying gain is set to proportional operational amplifying. Currently, we can use meter amplifier, which usually can meet the high CMRR demand and has adjustable gain, while the separate operational amplifiers can also be used.ECG signal is a low-frequency signal hidden in much strong interference and noises, such as my opotential interference, power-line interference, amplifier noise and the noise between electrodes and skin, whose lowest frequency is under 1Hz. Accordingly, the filtering and anti-power-line interference circuits are very important circuits among the whole design solution, while designing filtering circuit, the key point is the match between resistance and capacitance.Central control module adopts single-chip AT89C52 with low power consumption as the main controller. The main controller is responsible for the coordination among each module and the sampling and processing of ECG signals. Concerning the single-chip software design, we chose the modularization software design method to write and debug the ECG signal sampling program, ECG data processing program, R-wave detection program, ECG signal abnormality analysis program, and so on.Wireless data transfer module uses PRT2000, which is a super-small wireless data transfer module with low power consumption and high speed, capable of receiving and sending data. This chip uses 433MHz IGM frequency band, which is a real integrated single-chip UHF chip that can receive and send data wirelessly. Furthermore, PTR2000 supports parallel data transfer, which provides convenience for circuit design. Its interface to client is the single-chip computer's parallel port and its interface to server is the PC's parallel port, but needs a RS232 voltage level transformation circuit.After finished hardware circuit design and software programming, we debugged and tested the integrated equipment. As for the ECG signal sampling, we tested the removal of right driving electrode, addition of left driving electrode, shield of ECG signal sampling module and the processing of sampled ECG data. From the testing, we found that the ECG signal sampling module can effectively suppress noise interference and picked high-quality ECG signals. After the sampled ECG data were processed, the quality of ECG signals would be improved further. Regarding the ECG signal R-wave detection and abnormality testing, we actually tested the ECG signals of 4 subjects and the results showed that the accuracy of R-wave detection and abnormality testing is very high and can meet the requirements of system.About the testing of wireless data transfer module, we tested the electrocardiogram under several different distances scenarios. The test results show that waveform is relatively clear in the 50M distance, which requires that subjects should not be out of the 50M area. So we still has a long way to go on wireless data transfer. To extend the transfer distance, we can increase the signal emitting power through power amplifier; or change communication method, such as GPRS, to cover a bigger area. In summary, our objective is to: 1) solve the ECG real-time monitoring problem for inpatients, 2) realize the ECG signal real-time sampling, transfer and monitoring of home patients on one platform, so achieve the hospital ECG information management Informatization. This system provides a good platform for doctors to dynamically observe patients and cure progress, and improve their ability to diagnose related diseases. It not only can mitigate patients'pains, but also can make good sense for improve hospital service. The ECG wireless transfer significantly shortens the interval between heart attach occurrence and emergency treatment, provide patients much more room to move about while ensuring patients'safety. Real-time monitoring transfers the heart-monitoring task to monitor, release patients from keeping worrying heart attack and improve their comfortable feeling.Consequently, there is certain gap between this thesis and the final objective. We should carry further research in the future and the main directions are server's comprehensive data processing module and high-performance wireless communication technology, in the author's opinion.