本文選題：有源電極 + 生物電��； 參考：《南方醫(yī)科大學》2012年碩士論文

【摘要】：人體的生物電信號(Bio-potential)與人體的許多功能密切相關,廣泛應用于臨床診斷、監(jiān)護以及疾病預防等方面。但是由于人體生物電的幅值十分微弱,同時存在的各種干擾信號幅值往往很大,因此要準確的獲得生物電信號必須通過專門的生物電傳感器。生物電傳感器一般是通過兩個步驟將人體生物電信號轉變?yōu)殡娐分须娦盘柕模菏紫入姌O收集淹沒于各種噪聲與干擾中的人體表面的微弱電勢變化,然后將檢測到的電勢變化傳輸?shù)椒糯箅娐?經過放大器電路濾除各種噪聲和干擾并且放大我們需要的微弱人體生物電信號,從而得到可供肉眼觀察的電勢變化波形。 目前生物電在便攜式設備與腦-機接口(Brain Computer Interface, BCI)領域的研究與應用在國內外掀起了一陣研究熱潮。但是由于傳統(tǒng)的人體生物電傳感設備體積較大并且需要較為苛刻的使用環(huán)境,不能滿足這些場合的應用。為了盡可能的減少環(huán)境限制,擴大人體生物電信號的使用范圍,設計一種體積小、功耗低、放大倍數(shù)高的新型生物電傳感放大設備顯得十分必要。其中新型電極和新型的前置運放的設計又是其中研究的重點。 傳統(tǒng)的濕電極在使用時需要去除皮膚角質層并且添加額外的導電膏和固定膠帶才能得到較好的信號,這樣既不方便也不令人舒適從而限制了生物電的應用范圍。對于新型電極的研究主要是為了克服傳統(tǒng)濕電極的不足,即固定方便并且無需額外的預處理。其典型的代表有源電極(Active Electrodes)和干電極(DryElectrode)。國外如Biosemi公司、Nuroscan等公司都有自己專利的電極以及配套系統(tǒng),而國內尚無較好的產品。 傳統(tǒng)的前置放大電路一般是針對臨床條件下或者使用者靜止的情況下設計的。而生物電的新型應用往往是處在人體運動狀態(tài)下或者惡劣的電磁環(huán)境下,因此,新型放大電路應該具備抗干擾、噪聲低、功耗低、電源穩(wěn)等特點。針對這些要求,新型前置放大電路的研究主要尋求三方面的突破：其一,進一步提電路的抗干擾能力；其二,尋求一種可靠的低功耗的電池供電方案；其三,能夠方便地與新型電極以及后續(xù)數(shù)字電路相結合。 本文的主要工作是設計了一種新型的生物電傳感采集顯示方案,包括電極、前置放大電路以及后續(xù)數(shù)字采集顯示系統(tǒng)的設計。對于電極的設計,針對實際情況與成本控制,本文選擇了較易實現(xiàn)的有源電極方案,整個電極選用直徑為1mm的純銀線與低成本的集成運放TLC272制作。對于前置放大電路的設計,本文選用儀表放大器AD623與TLC1078/1079兩種低功耗芯片以保證整個電路的低功耗水平；采用Spinelli等人提出的AC耦合方法,使得作為第一級放大的儀表放大器AD623能夠放大1000倍從而降低了整個系統(tǒng)的噪聲水平；利用右腿驅動電路(Driven Right Leg circuit, DRL)(?)將人體電勢驅動到供電電壓的一半以滿足單電源供電的需要。整個生物電傳感裝置較好地解決了電極阻抗不匹配產生的分壓效應問題,充分抑制并減小了共模電壓。整個模擬電路部分的設計采用仿真分析輔助實際電路實踐驗證的方法,即先在計算機中應用Pspice軟件模擬分析,然后再實際搭建電路驗證軟件模擬結果,取得了較好的效果。Pspice仿真實驗表明：該方案比其他幾種類型的放大方案具有更寬的頻帶和更高放大增益,其50Hz共模抑制比可達到120dB以上,能夠將μV級的信號放大至10000倍(受電源電壓限制)。在實際電路的心電信號采集的測試中(放大1000倍),能夠在沒有任何皮膚處理的情況下,通過普通示波器觀察到清晰明顯的標準Ⅰ導聯(lián)下的心電波形。對于腦電信號采集測試中(放大10000倍),采用DG1011型函數(shù)信號發(fā)生器內建的心電信號經阻性電路的衰減得到的信號進行模擬,也在示波器中得到了明顯的信號,這表明該方案能夠較好的抑制各種干擾噪聲,能夠在較惡劣的電磁環(huán)境中測量到人體微弱生物電信號。數(shù)字電路及顯示部分選用芯片STM32作為下位機,主要用于AD轉換以及與計算機的數(shù)字通訊,上位機程序選用LabVIEW軟件編寫,主要實現(xiàn)顯示功能。
[Abstract]:Human bioelectrical signal (Bio-potential) is closely related to many functions of the human body. It is widely used in clinical diagnosis, monitoring and disease prevention. However, because the amplitude of human bioelectricity is very weak, the amplitude of various interference signals is often very large. Bioelectrical sensors. Bioelectrical sensors generally convert the human bioelectrical signals into electrical signals in the circuit through two steps: first, the electrode collects the weak potential changes of the human body surface submerged in various noises and interference, and then transfers the detected potential changes to the amplifier circuit and filters out various kinds of electric circuits through the amplifier circuit. Noise and interference, and magnify the weak human bioelectrical signals we need, so that we can get the potential change waveforms for the naked eye.
At present, the research and application of bioelectricity in the field of portable equipment and Brain Computer Interface (BCI) has set off a surge of research at home and abroad. However, because of the large size of the traditional human bioelectrical sensing equipment and the need for a more harsh environment, it can not meet the application of these applications. It is necessary to design a new type of biological electrical sensing magnifying equipment with small size, low power consumption and high magnification. The design of new electrode and new preamplifier is the focus of the research.
The traditional wet electrode needs to remove the skin cuticle and add extra conductive paste and adhesive tape to get better signal. It is neither convenient nor comfortable to limit the application range of bioelectricity. The research of new electrode is mainly to take the deficiency of traditional wet electrode, that is, it is convenient and convenient to fix. There is no need for extra pretreatment. It typically represents the active electrode (Active Electrodes) and dry electrode (DryElectrode). Foreign companies such as Biosemi, Nuroscan and other companies have their own patent electrodes and supporting systems, but there are no better products at home.
The traditional preamplifier circuit is usually designed under the condition of clinical or user static. The new application of bioelectricity is often under the condition of human motion or in the harsh electromagnetic environment. Therefore, the new type of amplifier should have the characteristics of anti-interference, low noise, low power consumption and stable power. The research of the new preamplifier mainly seeks three breakthroughs: one is to further improve the anti-interference ability of the circuit; secondly, to seek a reliable and low power battery power supply scheme; thirdly, it can be easily combined with new electrodes and subsequent digital circuits.
The main work of this paper is to design a new type of bioelectrical sensing collection and display scheme, including the design of electrode, preamplifier circuit and subsequent digital acquisition and display system. For the design of the electrode, in view of the actual situation and cost control, this paper selects the active electrode scheme which is easier to realize. The diameter of the whole electrode is 1mm. The pure silver line and low cost integrated operational amplifier TLC272 are made. For the design of the preamplifier circuit, the instrument amplifier AD623 and TLC1078/1079 two low power chips are selected to ensure the low power consumption level of the whole circuit. The AC coupling method proposed by Spinelli et al. Makes the AD623 of the instrument amplifier as the first stage magnification can be magnified The noise level of the whole system is reduced by 1000 times, and the right leg drive circuit (Driven Right Leg circuit, DRL) is used to drive the potential of the human body to half of the power supply to meet the needs of the single power supply. The whole bioelectrical sensing device solves the problem of the partial pressure effect caused by the mismatch of the electrode resistance, and fully restrains it. The common mode voltage is reduced. The design of the whole analog circuit uses the method of simulation analysis to assist the practice verification of the actual circuit, that is to use the simulation analysis of Pspice software in the computer first, and then build the circuit to verify the results of the software simulation, and obtain good results.Pspice simulation experiments show that the scheme is more than the other types. The amplification scheme has a wider frequency band and higher amplification gain, and its 50Hz common mode suppression ratio can reach more than 120dB and can magnify the signal of the V level to 10000 times (subject to the power supply voltage limit). In the test of the ECG signal acquisition in the actual circuit (magnified 1000 times), it can pass the ordinary oscilloscope without any skin treatment. The ECG waveform under the clear and obvious standard I lead is observed. For the EEG signal acquisition test (10000 times magnified), the signal obtained by the attenuation of the impedance circuit built by the DG1011 type function signal generator is simulated, and the obvious signal is obtained in the oscilloscope, which shows that the scheme can be better suppressed. Various interference noises can be used to measure the weak bioelectrical signal of human body in a bad electromagnetic environment. The digital circuit and display part are used as a lower computer, which is mainly used in AD conversion and digital communication with the computer. The host computer program is written by LabVIEW software, which mainly realizes the display function.

【學位授予單位】：南方醫(yī)科大學
【學位級別】：碩士
【學位授予年份】：2012
【分類號】：R318.6

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本文編號：1805744