脉搏传感器及电路设计[中文5384字]【中英文WORD】.zip

收藏

压缩包目录 预览区
  • 全部
    • 脉搏传感器及电路设计[中文5384字]【中英文WORD】
      • 脉搏传感器及电路设计[中文5384字].doc--点击预览
跳过导航链接。
折叠 脉搏传感器及电路设计中文5384字中英文WORD.zip脉搏传感器及电路设计中文5384字中英文WORD.zip
展开 脉搏传感器及电路设计[中文5384字]【中英文WORD】脉搏传感器及电路设计[中文5384字]【中英文WORD】
请点击导航文件预览
编号:7706829    类型:共享资源    大小:20.19KB    格式:ZIP    上传时间:2024-04-25
8
金币
关 键 词:
中文5384字 中英文WORD 脉搏 传感器 电路设计 中文 中英文 word
资源描述:
1译文:译文:脉搏传感器及电路设计 脉诊具有 2600 多年临床实践,是我国传统中医四诊中的精髓。脉搏信息在中医、西医中都有着十分重要意义。在传统中医脉诊中,切脉技巧复杂难以掌握和运用,医生主观因素影响也较大,随着科学技术的发展,PVdF(聚偏二氟乙烯)压电薄膜的研制确定了不同的脉象仪用于脉诊的客观化,本设计的脉象仪传感器的敏感部分是人手指。本文将从模拟中医脉诊的角度,研制了 PVdF 压电位体积能获得大的输出功率。因为换能器单位体薄膜传感器,并应用于脉象仪研究。积最大输出功率正比于机电耦合系数和能承受的定量化已成为中医诊断的必然趋势。几十年来,国家选择 PVdF 压电薄膜,因为它有如下几个的优点:首先,膜轻且柔韧,易于制备,与人体组织的阻抗耦合性好,能紧贴皮肤,使得脉搏信号通过薄膜而不失真。另外由于薄膜类似于人类皮肤,可以制作仿生触觉传感器。压电常数大(d33=20 pC/N),变力易于研究,但从研制情况看,大部分传感器不能模拟中敏度。比石英晶体高 10 倍,压电电压输出常数切脉时所取三部,按、浮、寸三种诊法,g=174 是所有压电体中最高的。检测脉搏信号,主要靠压力定标,适用性不够好。其次,机械品质因素低,阻尼小,密度低,具有宽带特性,能满足脉搏信号的频率特性。在非常高的交变电场中不至于去极化。由于 PVdF 膜的柔性及其厚度方向伸缩振动的谐振频率很高,使得在很宽范围内有平坦的频率。基于 PVdF 膜的以上优点,根据中医切脉模式,我们研制出了三点式的传感器,三个换能器分别由 PVdF 薄膜作成正方形片状,面积相当于切脉时指腹的受力面积,在压电薄膜电荷生成的两极分别蒸镀铝电极并引出导线,用柔性有机塑料薄膜封装并做成圆形基片,装在一根表带上。考虑到患者体征、老幼等因素,三个换能器独立地对应于按、浮、寸三个部位,且能在表带上纵横调节。测量时表带束在腕部,医生手指对应的放大三个换能器即可。医生可以透过薄片感觉到脉搏的波动。根据浮、中、沉模式把脉过程中可以人为地控制力度,做到因人而异克服以往缸体换能器压力定标所取浮不足。当周期性脉搏压力作用在换能器上时,将机械能转换为电能。脉象频谱分析表明脉象能谱中 99%的能量集中在 10 Hz 以下,最高频率不超过 40 Hz。调实现与微机的通信。PVdF 压电薄膜换能器是本设计中的敏感部件,也是设计的关键环节之一,作用是能模拟其中人的压觉,将微弱低频的脉搏压力信号转换成电信号。设置前置电荷放大器作用有二:一是与换能器阻抗匹配,把高阻抗输入变为低阻抗输出;二是将微弱电荷转换成电压信号并放大。为了提高测量的精度和灵敏度,前置放大电路采用了线性修正的电荷放大电路,以获得较低的下限频率,消除电缆的分布馈电容。电容对灵敏度的影响,使设计的传感器体积小型化。第一个低通滤波电路由 R1 和 C1组成,截止频率约为 1000Hz,以使脉搏信号的高次谐波能通过,让脉搏信号反映的病理性特征信息得到完整的保留。同时该上限截止频率和时间常数电路(由 C2 和 R2 组成)还会决定性地影响脉搏波形的失真度。如果电路的时间常数选得过小,会造成信号的低频分量严重衰减和移相。实验表明,当时间足以保证脉搏波的低频分量不会失真。电压放大器主要是对电荷放大器输出的电压信号放大。并提供不同的增益。根据我们的经验,设置上限截止频率为 100Hz比较理想。工频陷波器环节是为了滤除市电 50HZ 干扰。电容应选钽电容作补偿电容,对市电噪声采取了硬件工频陷波和软件滤波并用的措施,实验证明,利用数字滤波技术,对工频干扰信号的抑制效果较好,对电磁信号抑制主要采取了2两种方法,一是对信号线进行屏蔽,二是设计四阶巴特沃斯低通滤波器,截止频率为 100 Hz。对于人体的抖动噪声主要是通过软件滤波加以滤除,主要是采用了防脉冲干扰平均值滤波法。该算法在凌阳单片机内实现,其基本思想是把测量得到的 256 个数据看成一队列,每进行一次新的测量,就把测量结果放入队尾,而剔除原来队首的一次数据,这样在队列中始终有 256 个“最新”数据,对 256 个数据逐个比较大小,去掉其中的最大值和最小值,然后计算 254 个数据的平均值。这种滤波方法对周期性干扰有良好的抑制作用,还能对滤除脉诊过程中人体偶尔的抖动产生的干扰。实验中发现,尽管人的体温基本保持恒定,但手腕部位皮肤表面的温度受外界温度变化的影响仍很大,而且手腕部位皮肤与传感器表面的温差也会给测量带来很大影响,需要消除温度效应利用人体脉搏(1 Hz 左右)热电噪声信号。由于人体的脉搏信号具有频率低、幅度小干扰大,不稳定度低,随机性强等特点,使得对脉搏信号的采集放大电路的设计提出了很严格的要求,尤其是抗干扰变为十分重要,需要设计低通滤波器进行滤波。选择放大器时需要从增益、频率响应,输入阻抗,共模抑制比,噪声,漂移等几个方面加以综合考虑。(1)抗干扰 首先,工频 50HZ 干扰及其各次谐波 使用频率为 50HZ 的市电的电子仪器设备会对检测系统会产生较大的干扰,其幅值大约是脉搏信号峰峰值的 50%,是主要的干扰源;其次,肌电干扰 肌肉的收缩会产生微伏级的电势,其幅值大约是脉搏信号峰峰值的 10,维持时间大约是50ms,频带范围可以在 0HZ10000HZ;再次,由于呼吸引起的基线漂移和 ECG 幅度变化 呼吸引起的基线漂移可以看成是一个以呼吸的频率加入 ECG 信号的窦性成分(正弦曲线),这个正弦成分的幅度和频率是变化的。呼吸所引起的 ECG 信号的幅度的变化可以达到 15。基线漂移的频率是从 0.150.3HZ。(2)低噪声、低漂移 在脉搏信号放大器中,由于增益较高,噪声和漂移是两个较重要的参数。脉搏信号放大器运行过程中的噪声主要表现为电子线路的固有热噪声和散粒噪声,这些都属于白噪声,其幅值为正态分布。为了获得一定信噪比的输出信号,对放大器的低噪声性能有严格要求。另外,温度变化会造成零点漂移,漂移现象限制了放大器的输入范围,使得微弱的缓变信号无法被放大。而脉搏信号具有很低的频率成分,为了能正常测量,必须采取措施来限制放大器的漂移。所以放大器应选用低漂移,高输入阻抗并且具有高共模抑制比的集成运放电路。其它传感器的比较 首先,压电式传感器 目前常用的是一次性心电电极,它是用印刷方法制得的 Ag/Agcl 传感器。这种传感器采用接扣与敏感区分离的方法,能明显的减少由于人体运动产生的干扰。电极的好坏对采集到的心电信号质量起着至关重要的作用,采用的电极应有贴力强,能紧附在人体表面,柔软、吸汗、极化电压低、导电性良好等特点。当选用电极传感器时,需要 3 个电极分别置于左右手和左腿,构成标准导联。临床上为了统一和便于比较所获得的脉搏信号,在检测脉搏信号时,对电极的位置,引线与放大器的连接方式都有严格的统一规定。目前市场上有一种采用新型高分子压电材料聚偏氟乙烯研制的压电传感器,其灵敏度高,频带范围好,结构简单,便于使用。当手指前端受到轻微的压力时,可以感觉到手指前端在血压的作用下有一张一弛的感觉,将这个信号用传感器提取出来,转变为电信号,通过指脉的波形检测,就可以获得人体的脉搏信号。其次,光电式传感器 血液是高度不透明的液体,光照在一般组织中的穿透性要比血液中大几十倍,据此特点,采用光电效应手指脉搏传感器来拾取脉搏信号。反向偏压的光敏二极管,它的反向电流具有随3光照强度增加而增加的光电效应特性,在一定光强范围内,光敏二极管的反向电流与光强呈线性关系。指端血管的容积和透光度随心搏改变时,将使光电三极管极管收到不同的光强,并由此产生的光电流均随之作相应变化。常用检测脉搏的光电传感器分为红外对管和红外放射管。采用红外对管,将对管夹于手指端部,通过手指的血液浓度会随着心脏的跳动发生变化,红外对管对应的信号便会发生相应的变化,采集此信号经过放大,滤波,比较等处理便可以得到理想的信号。采用反射式的红外管。现在市场上的心率计普遍采用这种传感器来采集信号,因为此红外管接收和发射都在手指的同一侧,因此便不用考虑每个人手指情况不同所造成的麻烦。接收的是血液漫反射回来的光,此信号可以精确地测得血管内容积变化。再次,集成传感器 当前,市面上有很多类型的集成心电传感器,其灵敏度高,集成度高,直接就可以反映出心率的变化,且已包含了滤波等抗干扰电路,波形经过放大可以直接处理使用。缺点是价格非常昂贵,一般均在五百元以上,就本次设计来说,考虑到经费以及锻炼自己的目的,不选择使用该型传感器。光电式优点是灵敏度高,易于操作,响应速度快,结构简单。但缺点是 1、外部光源的变化对测量结果的影响较大;2、需要购买专门的医用光电传感器,价格较贵且不易购买;3、对这样的器件接触很少,对其进行调试时可能会出现较大困难。压电式优点是结构简单,实时性好,工作频带宽,应用电路简单,且价格低廉。但缺点是直接与人体相接触,容易因为人体肌肉的颤动等而产生干扰,并且容易受到外界其他信号的干扰。集成式优点是集成度高,包含了滤波,放大电路,可以直接输出信号,便于操作,有效的减少了各种干扰。但缺点降低了本任务的难度,如果采用该传感器,只需将其直接接上单片机即可实现功能,且价格非常昂贵。考虑到种种情况,结合本系统的设计要求以及经费的考虑,最终选择压电薄膜脉搏传感器。该传感器价格较低,而且输出电压变化较为明显,可以实现我们的实验目的。压电薄膜脉搏传感器包括三个部分,镀银层、压电陶瓷以及铜片。外部压力作用于铜片时,压电陶瓷就可以感受压力而产生电信号,并最终通过镀银层将该信号输出。在使用时,压电陶瓷片要通过导线与电路板连接,注意在焊接压电陶瓷片时,时间不能太长以免烫坏压电陶瓷片的镀银层。由于压电陶瓷片的资料比较少,为了确定使用该传感器能够实现本次设计的目的,先要对其进行实验,来确定它的输出电压是否符合要求。由于只需要 4mv-5mv 左右的电压输出,就可以实现设计要求。由试验,可以得知压电陶瓷片可以实现我们所要达到的目标。整体电路分析 经实验可知,采用 GaAs 红外发光二极管作为光源时,可基本抑制由呼吸运动造成的脉搏波曲线的漂移。脉搏波检测以光电检测技术为基础,因此受周围杂散光、暗电流等各种干扰影响较大,为了克服这一问题本系统采用脉冲振幅光调制技术。脉冲调制传送的是调制信号的采样值,只要采样频率奈奎斯特采样频率,则可由采样脉冲来恢复原信号,而不会导致失真。系统对红外二极管的驱动脉冲信号的频率选定为工频整数倍 400Hz 以降低工频干扰,脉冲载波由ADuC841 内部 16 位数模转换器产生。为了保证红外发光二极管的光源稳定,本文采用运放 op495和 NPN 型三极管作为恒流源电路向发光二极管提供稳定的工作电流。光敏二极管的特性是将光信号转换为电流,而随后的 A/D 转换电路是以电压为检测对象。因此,接收电路中应采用电流电压变换电路,将电流信号转换为电压信号。运算放大器与电阻 R形成电流电压变换电路,如图 4-2 所示。(图中 S_GND 为信号地,运算放大器工作正负电源为 5V、40V,为避免信号丢失,将信号抬高至 VS_GND=1V)电路输出电压。由于光电脉搏波属于缓慢变化的微弱生理信号,信噪比低,极易受到环境噪声和肢体运动的干扰。传统的光电脉搏波信号检测电路都采用高增益放大器,以获得较高的检测灵敏度,这种设计思路导致了检测信号动态范围缩小,在受到运动干扰时,将导致由于干扰信号而带来的光电脉搏波信号检测的饱和失真。本系统采用过采样技术,通过对信号的高速采样来提高采样精度,相当于用高分辨率的 ADC 对信号进行模数转换,达到了提高信噪比并改善动态范围的效果。因此对经过光电转换后的信号进行模数转换而不需要任何信号调理(放大和滤波)电路。所谓过采样技术是指以远远高于奈奎斯特(Nyquist)采样频率的频率对模拟信号进行采样的方法。由信号采样量化理论可知,若输入信号的最小幅度大于量化器的量化电平,并且输入信号的幅度随机分布,则量化噪声的总功率是一个常数,在 0fs2 的频带范围内均匀分布。因此量化噪声电平与采样频率成反比,如果提高采样频率,则可以降低量化噪声电平,而由于基带是固定不变的,因而减少了基带范围内的噪声功率,提高了信噪比,从而提高分辨率,并且采样频率每提高 4 倍,则信噪比提高 4 倍,相当于 A/DC 的分辨率提高 1 位。滤波器为一个数字低通滤波器,主要是滤除采样信号频带以外的高频量化噪声,并维持信号频带以内的信号基本不变,抽取是将采样得到的高速低分辨率的数字信号的抽样频率降至奈奎斯特采样频率,进而完成高分辨率数字信号的重构,抗混叠主要是滤除降低取样频率后可能出现的混叠噪声。数字滤波和抽取均通过软件来实现,配置灵活。传感器主要由红外线发射二极管和接收二极管组成,测量的原理如下:将手指放在红外线发射二极管和接收二极管中间,随着心脏的跳动,由于手指放在光的传递路径中,血管中血液饱和程度的变化将引起光的强度发生变化,因此和心跳的节拍相对应,红外接收二极管的电流也跟着改变,这就导致红外接收二极管输出脉冲信号。脉冲信号由 F1F3、R3R5、C1、C2 等组成的低通放大器进行放大,再经由 F4、R6、R7、C3 组成的放大器进一步放大,其输出信号送给由 F5、F6、RP1、R8 等组成的施密特触发器进行整形后输出,输出的脉冲信号作为单片机的外部中断信号。可变电阻 RP1 用来调整施密特触发器的阀值电压,从而调整电路的灵敏度。AT89C2051、X1、R10、C5 等组成单片机电路,单片机电路对 P3.2 输入的脉冲信号进行计算处理后把结果送到数码管显示,发光二极管 VD3 作脉搏测量状态显示,脉搏每跳动一次发光二极管就点亮一次,数码管 DS1DS3、VT1VT3、R12R21 等组成数码显示电路。本机P3.3-P3.5 口作三个数码管的动态扫描位驱动码输出,通过三极管驱动数码管,P1.0-P1.6 口作数码显示七段笔划字形码的输出,用以驱动数码管的各字段。原文:原文:Pulse transducer and circuit design Pulse has 2600 years of clinical practice,is the essence of the four diagnostic methods of traditional Chinese medicine.Pulse in traditional Chinese medicine,Western medicine has a very important significance.The Qiemo skills in traditional Chinese pulse diagnosis is difficult to grasp and apply the doctors subjective factors,along with the development of science and technology,PVdF(polyvinylidene fluoride)piezoelectric film developed to determine the different pulse instrument the objective of the pulse,the sensitive part of the design of the pulse instrument sensor finger.This article from the perspective of the analog pulse diagnosis,the development of PVdF piezoelectric volume to obtain a large output power.Because of the change of unit-body thin film sensors,and applied to the pulse instrument.Plot the maximum output power is proportional to the electromechanical coupling coefficient and able to withstand the quantitative has become the inevitable trend of Ch5inese medicine diagnosis.Decades,the state selected PVdF piezoelectric film,because it follows several advantages:First,film light and flexible,easy preparation and human tissue impedance coupling can be close to the skin,without distortion of the pulse signal through the film.In addition,the film is similar to human skin,you can create a biomimetic tactile sensor.The piezoelectric constant(d33=20 pC/N),the inotropic easy to study,but the development of the situation,most of the sensor can not be simulated in the sensitivity.10 times higher than the quartz crystal,the piezoelectric voltage output constant Qiemo take three,floating,three diagnostic methods,g=174 is the highest of all the piezoelectric.Detection pulse signal depends mainly on the pressure calibration,the applicability is not good enough.Then,mechanical quality factor low,damping,low density,with broadband features to address the frequency characteristics of the pulse signal.If not depolarization in the very high alternating electric field.PVdF membrane flexibility and its thickness direction of the stretchingvibration of the resonant frequency is high,making a wide range of flat frequency.PVdF membrane above advantages,according to Chinese medicine Qiemo model,we developed a three-sensor,three square sheet made by the PVdF film transducer,an area equivalent to the force the Qiemo when pulp area in the piezoelectric film bipolar charge generated steam the aluminum electrode and leads to the wire,flexible organic plastic film packaging made of a circular substrate,mounted on a table to bring.Taking into account the patients signs,young and old,and other factors,the three transducer independently corresponds to the vertical and horizontal adjustment by floating an inch three parts,and can bring in the table.Strap-beam measurements in the wrist,and the doctor finger corresponding to enlarge three transducers can.The doctor can feel through the thin slices pulse fluctuations.Floating,mode pulse process can artificially control the intensity,do vary from person to person to overcome the pressure of the past cylinder transducer calibration taken floating inadequate.When a periodic pulse pressure transducer,mechanical energy converted to electricity.The pulse spectrum analysis shows that 99%of the energy in the pulse spectrum is concentrated below 10 Hz,the highest frequency of no more than 40 Hz.Tune to achieve communication with the computer.PVdF piezoelectric film transducer is sensitive components in this design,is also designed one of the key links of the role of simulation in which the pressure sensation can,will the pulse pressure of the weak low-frequency signal conversion into electrical signals.Set of pre-charge amplifier role there are two:First,with the transducer impedance matching,high-impedance input into a low impedance output;second is the weak charge into a voltage signal and zoom.In order to improve the measurement accuracy and sensitivity,pre-amplifier circuit using a linear correction of the charge amplifier to lower the lower limit frequency,eliminating the cable distribution of feed-forward capacitor.Capacitance on the sensitivity of the impact of the design of the small sensor size.The first low-pass filter circuit formed by R1 and C1,the cutoff frequency of about 1000 Hz,so that the higher harmonic of the pulse signal through the pulse signal reflected pathological feature information to get the full reservation.While theupper limit cut-off frequency and the time constant circuit(formed by C2 and R2)will decisively influence the distortion of the pulse waveform.If the circuit time constant is selected too small,will cause a serious low-frequency component of the signal attenuation and phase shift.The experiments show that when the time sufficient to ensure that the pulse wave of low frequency components without distortion.Voltage amplifier,the charge amplifier output voltage signal amplification.And provide different gain.According to our experience,set the upper cut-off frequency of 1006Hz.Power frequency notch filter link in order to filter out the mains 50HZ interference.Capacitor tantalum capacitor should be selected for the compensation capacitor,hardware power frequency notch and software filtering and measures taken to the city electrical noise,experimental results show that the use of digital filtering techniques,the inhibitory effect of frequency interference signals better electromagnetic signal suppression has mainly taken two ways,one signal line shield is designed for fourth-order Butterworth low-pass filter cutoff frequency of 100 Hz.Jitter noise for the human body mainly through the software filter to filter out,mainly using the anti-pulse interference average filtering method.Sunplus,the algorithm implementation,the basic idea is that the 256 data measured as a queue,each time a new measurement,put the measurements into the tail,and remove the original team the first time data,such there is always 256,the latest data in the queue size,256-by-comparison data to remove the maximum and minimum,and then calculate the average of 254 data.This filtering method for periodic interference of inhibition,but also occasionally filter out the pulse of human jitter generated interference.Found that,despite the persons body temperature is kept constant,but the wrist skin surface temperature of the outside temperature changes still,and the skin of the wrist with the sensor surface,the temperature difference will have a great impact to the measurement requires the elimination of The temperature effect of the use of human pulse(1Hz)Thermal noise signal.As the body of the pulse signal has a low frequency,amplitude interference,instability,randomness,and other characteristics,makes very strict requirements on the acquisition of the pulse signal amplifier design,especially the anti-interferencebecomes very important,need to design low-pass filter for filtering.Select amplifier from the gain,frequency response,input impedance,common-mode rejection ratio,noise,drift,several aspects to be taken into account.(1)anti-jamming First,power frequency the 50HZ interference and its harmonics The use of frequency 50HZ electricity electronic equipment devices can cause detection system will have a greater interference,and its amplitude is about 50%of the pulse signal peak to peak,is the main source of interference;Then,EMG interference The contraction of the muscle will produce microvolt potential,its amplitude is about 10%of the pulse signal peak to peak hold time is 50ms,the frequency range in 0HZ 10000HZ;Finaly,breathing caused by baseline drift and ECG amplitude variations Breathing caused by baseline drift sinus component(sinusoidal)can be seen as a respiratory frequency by adding the ECG signal,the amplitude and frequency of this sine components of change.Breathing caused by changes of the ECG signal amplitude can reach 15%.The baseline drift of the frequency from 0.15 0.3HZ.(2)low noise,low drift Pulse amplifier,high gain,noise and drift are the two important parameters.Noise in the pulse amplifier running the electronic circuit of the inherent thermal noise and shot noise,these are the white noise,the amplitude for the normal distribution.In order to obtain a certain signal to noise ratio of the output signal,the amplifiers low noise performance,there are strict requirements.In addition,the temperature change will cause zero drift,drift limits the amplifiers input range,the weak slowly varying signals can not be enlarged.The pulse signal has a very low frequency components to normal measurements,measures must be taken to limit the drift of the amplifier.Therefore,the amplifier should use low drift,high input impedance and high common mode rejection ratio of the integrated operational amplifier circuit.Other sensors First,piezoelectric sensor Currently used disposable ECG electrodes,which is obtained by printing methods Ag/Agcl sensor.This sensor uses the method of separation then buckle sensitive areas,can significantly reduce 7the interference due to human movement.Electrode The quality of the collected ECG signal quality plays a vital role,using the electrode should be posted strong,can be tightly at
展开阅读全文
提示  点石文库所有资源均是用户自行上传分享,仅供网友学习交流,未经上传用户书面授权,请勿作他用。
关于本文
本文标题:脉搏传感器及电路设计[中文5384字]【中英文WORD】.zip
链接地址:https://www.dswenku.com/p-7706829.html
关于点石文库 - 投资与合作 - 会员权益 - 联系我们 - 声明 - 人才招聘

点石文库上传QQ群: 862612017    侵权投诉客服QQ:3339525602  下载帮助客服QQ: 3339525602 

点石文库版权所有  联系邮箱:3339525602#qq.com (请把#改为@)

 工信部备案号:湘ICP备19015001号-1

收起
展开