The Non-contact Sleep Ecg Measurement System Based On Conductive Fabric Design

Based on the new developing requirements of sleep monitoring at present, using ECG and other physiological parameters to replace the signal of EEG for the analysis of sleep state has become an important research field.The equipment made by this design needs to provide the necessary data for adjusting the matching sleep treating instrument. Taking into account of both the comfort and the measurement accuracy in this design, we adopt a new approach, non-contact monitoring based on conductive fabric, for extraction, identification and analysis of ECG signal. And then, we judge whether the results are suitable for monitoring the sleep stages. The non-contact ECG signal acquisition can be used easily and for a long time, which is suitable for the use in household measuring systems and community hospitals. We use the CC2500wireless transmission module for communication between the signal acquisition components and processing components. So the system reduces the requirements of the using environment.This design is mainly responsible for providing a complete hardware platform as well as some software functions to the sleep ECG measuring, including non-contact ECG acquisition part, the ECG signal conditioning circuits, the hardware and software design for the embedded system as well as part of the PC software for features and algorithms. We should complete the design of prototype of the non-contact ECG measuring system finally, verify the accuracy and reliability of the system through actual tests by human being.The emphases of this design are the following aspects.1) We should design the ECG signal conditioning circuits. Considering the comfort, which is necessary for the stages of sleep, we use conductive fabric to replace the patch electrode for signal acquisition. Taking into account that we don’t use the fixed conductive adhesive or medical hydrogel polarity electrodes and the fabric itself has characteristics of high impedance and deformation, we need to design better ECG conditioning circuits. The design done in this project, which can meet requirements better, contains the preamplifier circuit, right-leg drive circuit, high-pass filter circuit, low-pass filter circuit, trap filter, main amplifier and level adjustment circuit. In the design phase, we use Multisim software for functional simulation and the Protel for circuit boards drawing.2) In order to realize the applications, such as the A/D acquisition and wireless transmission in the embedded system, we build this system using the LPC2148chip. So we can use it for signal acquisition, data processing and data transmission using wireless modules instead of data line. We design the topology of embedded system based on functional requirements and parameter indexes. And then, we should finish the hardware design and software development.3) This system needs to match a variety of sleep ECG algorithms. So it is necessary for the PC software to extract the ECG information effectively. By optimizing the hardware circuits and software algorithms, this design can record the whole band waveform of sleep ECG. So, this design provides a good platform for the analysis of sleep.Finally, we finish the design of the non-contact measuring system’s prototype, measure the sleep ECG, describe the problems encountered in the debugging stage and the solutions, show the prototype and the photos of measured waveform.