ecg心电图英语翻译

ecg心电图英语翻译 Typical ECG Signal Chain Figure 2 shows a block diagram of a typical single-channel electrocardiograph. In that chain it is apparent that all filtering is done in the analog domain, while the microprocessor, microcontroller, or DSP is used principally for communication and other downstream purposes. Thus the powerful computational properties of the digital core are not readily available to deal with the signal in its essentially raw state. In addition, sophisticated analog filters can be costly to the overall and the space, cost, and power they design due to their inflexibility— require. Proposed Circuit The signal chain can be simplified by using an ADuC842 MicroConverter, which allows the ADC, filters, and microprocessor to be combined in a single integrated circuit. Additional advantages are flexibility of filter implementation and isolation in the digital domain. The proposed system design is shown in Figure 3. Analog Input Processing The analog front end uses the typical approach with an instrumentation amplifier (IA) and a right leg common-mode feedback op amp. The IA is the AD620, a low cost, high accuracy instrumentation amplifier, with excellent dc performance: CMR>>100 dB to nearly 1 kHz, 50-µV max offset voltage, low input bias current (1 nA max), and low input voltage noise (0.28 µV from 0.1 Hz to 10 Hz). The AD620 requires only a single external gain-setting resistor, R. G Resistors R2 and R3 change the normal gain equation to [Gain = 1 + 49.4 k/R + (49.4 k/2)/22 k]. To avoid output saturation, the usable gain is G limited by the output swing and the maximum input voltage to the IA. With a ?5-V power supply, the output swing of the AD620 is about ?3.8 V; and the maximum input is ?5 mV plus a variable normal-mode dc offset of up to ?300 mV, allowing a maximum gain of 12.45. Here, the gain is conservatively set to 8 (?1%), using R = 8.45 kΩ. G The op amp used in the right-leg common-mode feedback circuit is the OP97, a low power, high precision operational amplifier with extremely high common-mode rejection (114 dB minimum). This circuit applies an inverted version of the common-mode interference to the subject’s right leg, with the aim of canceling the interference. The op amp has a voltage gain for the common-mode voltage of 91 [viz., R4/(R2 || R3) = 1 MΩ/11 kΩ], with a 1.6-Hz rolloff and a low-pass cutoff at about 160 Hz for stability [f– = 1/(2π × (10 kΩ × 0.1 µF)]. 3 dB 典型心电图信号链 图2显示一个典型的单通道框图心电图纸。在那个链很明显,所有的过滤做是模拟领域,whi乐微处理器, 使用单片机、DSP主要或进行交流和其他下游的目的。如此强大的计算性能的核心是不容易得到的数字处理信号在其本质上原始状态。此外,复杂的模拟滤波器的代价是昂贵的,由于他们的总体设计inflexibility-and空间因素、成本因素、权力的要求。 提出电路 simplif信号链可以用一个ADuC842的挑战MicroConverter,从而允许ADC、过滤器、和微处理器被合并成一个集成电路。附加优势过滤是灵活的实施和孤立的数字吗领域。该系统的设计是如图3。 模拟输入处理 仪表放大器(IA)和右腿模模拟前端采用典型的方法反馈运算放大器。AD620会所, 是低成本、高准确度amplif这样仪器,具有优良的直流性能: > > 100分贝至CMR 近1 kHz,50 - V最大偏移电压、低输入偏置电流(1钠马克斯),低输入电压噪声 (0.28 V从0.1赫兹到10赫兹). AD620的只需要单个外部gain-setting电阻, 鲁柏。 电阻R2和R3改变正常获得方程[收益= 1 + 49.4 k / RG +(49.4 k / 2)/ 22 k]。为了避 免输出饱和度、可用的获得是有限的,由的输出摆幅和最大输入电压的下风。用 5 v的电源AD620的输出摆幅的是关于3.8 V,最大值输入变量5 mV加上一 个normal-mode直流偏置的300 mV,允许最大收益的12.45。这里,增益保守的 设置为8(1%),RG = 8.45 k。运算放大器的用于right-leg模反馈电路OP97,是一 个低功率、高精密运算放大器吗以极高的共模抑制(114分贝最低)。该电路应用 一个倒模的版本干扰个体的右腿,目标是取消了干扰。运算放大器的增益有电压 为普通-模电压91年[农化表型(R2 | | R3)= 1 M/ 11 k]的-Hz rolloff 1.6和低通 截止大约在160赫兹的稳定性[f-3 dB = 1 /(2(10 k0.1F)]。 Digital Isolation Digital isolation is at the heart of the RS232 interface to the PC, which is suggested for the display in this example. The isolator is the ADuM1301, ?a bidirectional digital isolator based on Analog Devices iCoupler technology—a technology that eliminates the design difficulties commonly associated with optocouplers (uncertain current-transfer ratios, nonlinear transfer functions, etc.). It also achieves high data rates with lower power consumption than optocouplers. The ADuM1301 has three independent isolation channels, two of which are used here—one for transmitting, the other for receiving data. (A further capability of the ADuM1301—not required here—is the ability to enable/disable the input/output data.) The power supply for the measurement side of the ADuM1301 is taken from the ADP3607-5 booster/regulator, which provides a fixed 5-V output. The power for the PC side is totally isolated from the circuit. It can be taken from the PC (as it is here) or from a different source. Safe Power The isolated power is supplied by a battery, which is recharged in a charging station when not in use. To handle a bipolar input signal, a ?5-V dual supply is required for the AD620 and OP97. The ADP3607-5 booster/regulator and the ADP3605 inverter serve as a regulated dual supply that provides positive and negative regulated voltages from a single 3-V battery. The ADP3607 is a regulated-output switched-capacitor voltage doubler capable of providing up to 50 mA. Capable of operating from an input voltage as low as 3 V, it is offered in a version with the regulation fixed at 5 V (ADP3607-5)—the one used here. (It is also available in a form adjustable over a 3-V to 9-V range via an external resistor. It can produce an even larger positive voltage with an external pump stage consisting of passive components.) The ADP3605 switched-capacitor voltage inverter, with a regulated output voltage, is capable of providing up to 120 mA. It is offered with the regulation fixed at –3 V (ADP3605-3) or adjustable via external resistors over a –3-V to –6-V range. (An even larger negative voltage can be achieved by adding an external pump stage, as with the ADP3607.) A –5-V supply is needed, with an input voltage of +5 V, so R is set to 31.6 kΩ (?1%), using the equation, V = –1.5 R/9.5 kΩ. OUT Both supply voltages (?5 V) are generated by capacitive charge pumps, which cannot generate unsafe voltages—even under fault conditions—because they do not require any inductors. These devices also feature a mode, which allows the MicroConverter to power down shutdown the devices when the system is not in use. 数字隔离 这个显示的例子是数字隔离器，数字隔离器是位于连接到PC的RS232接口 的中 心。这种数字隔离器是ADuM1301，它采用的是一个双向的基于ADI公 司的 iCoupler技术，这种技术消除了与光电耦合器相关的一些普遍设计 困难(例如 不确定的电流传输比率，非线性传递函数等等)。 在低功耗的工作状态下，相比光电耦合器，数字隔离器能实现更高的数 据传输 率。ADuM1301有三个独立的隔离通道，这里用到的其中两个一个 是用于传送 数据，另一个是为了接收数据。(ADuM1301的另一个功能— —启用或禁用输入/ 输出数据——在这里是不需要的。)ADuM1301的电力 是取自ADP3607-5增压器 /调节器，它提供了一个固定的5V输出。PC端的 电源完全隔离电路。它可以从 PC端(就像这里)或者从不同来源获取。 用电安全 隔离的电力都是由电池组提供，在不使用时可以在充电站重新充电， 为了处理输入信号双极性问题，需要给AD620和OP97提供?5V的双向电压。 ADP3607-5升压器/校准器和ADP3605反相器充当3V电池正负双向电压调解。 ADP3607是一个调解输出开关电容倍压器，能够提供高达50mA电流，能够调解 使输入电压低至3V，ADP3607-5型号可以调节5V固定电压，在这里就是使用这 种型号(通过外部电阻可以有3~9V的调节范围。可以产生一个很大的正向电压 和一个外部脉动机制组成的无源元件)。在可控输出电压控制下，ADP3605开关 电容电压反相器能够提供高达120m电流。它可提供一个固定-3V电压 (ADP3605-3)或者通过调节外部电阻使其电压范围在-3V到-6V之间。(要得到 更大的反向电压可以通过增加一个外部泵获得，就像ADP3607)在输入电压为+5V 的情况下，一个-5V的电源是必要的，所以电阻R设置为31.6kΩ，利用公式可 得:电压V=-1.5R/9.5kΩ。两个电源电压(?5V)所产生的电容充电不会产生不 安全电压，即使在故障情况下，因为它们不需要任何电感。这些器件还具有一个 关机模式，使得当系统不在工作的状态下，单片机仍能为器件供电。 Patient Safety In addition to the digital isolation and the safe power supply, the series resistors, Rx1, Rx2, and Rx3, provide protection for the patient—in order to comply with AAMI (Association for the Advancement of Medical Instrumentation) standards for safe current levels ( References). see These standards require that rms ground currents or fault current from the electronics must be less than 50 µA. Signal Processing The ADuC842 MicroConverter is well suited for the main signal processing tasks. It features a fast, 12-bit ADC and other high-performance analog peripherals, a fast 8052 microprocessor core, integrated 62KB flash memory for code, and several other useful peripherals, as shown in Figure 4. The key components of the MicroConverter for this design are the ADC and the 8052 core. The ADC converts the analog output of the instrumentation amplifier to a digital signal. The software written for the 8052 core processes the digitized signal to produce the data for the ultimate ECG trace. As in many MicroConverter designs, the software includes both complex high level code written in C and time sensitive routines written in assembly code. In this case, the implementation of band-pass filters and notch filters is in C, while the ADC is controlled by assembly code. Assembly code, combined with converter speed, enables the accumulation of multiple samples, enhancing the effective resolution of the ADC well beyond its normal 12 bits. Figure 5 gives a good indication of the effectiveness of the MicroConverter. The top trace is the signal from the instrumentation amplifier applied to the ADC. The middle trace shows the initial results achieved using the C-code filtering only, while the bottom trace shows the final result after the processing of multiple conversions, using assembly code. 病人安全 除了数字隔离和安全供电，串联电阻，RX1，RX2，以及RX3，提供保护病人AAMI (医疗仪器促进协会)，以符合安全目前的水平(请参阅参考资料)。这些 标准要求，RMS接地电流或故障电流从电子必须小于50A。 信号处理 单片机非常适合信号处理的主要任务。它具有一个快速12位ADC和其ADuC842 它高性能模拟外设，一个快速的8052微处理器为核心，集成62KB代码闪存，和 其他一些有用的外围设备，如图4所示。这种设计单片机的关键部件是ADC和8052 的核心。 ADC转换为数字信号的仪表放大器的模拟输出。 8052核心编写的软件 处理的数字信号，产生最终心电图跟踪的数据。由于在许多单片机设计中，该软 件包括复杂的高层次的代码写在C和汇编代码编写的时间敏感例程。在这种情况下，带通滤波器，陷波滤波器的实施是在C，而ADC是由汇编代码控制。汇编代码，转换速度相结合，使多个样本的积累，提高远远超出了其正常的12位ADC的有效分辨率。图5给出了一个很好的迹象单片机的成效。顶部曲线是适用于ADC的仪表放大器的信号。中间的跟踪显示，实现使用的C代码，只过滤的初步结果，而底部的跟踪显示多个转换处理后的最终结果，使用汇编代码。 Filters in C Code The acquired signal is processed by digital filtering in the MicroConverter. For this purpose, we designed two second-order digital infinite impulse-response (IIR) filters, based on a sampling frequency of 500 Hz. A notch filter was designed to suppress the 50-Hz interference. The chosen design procedure was the , with a pole-zero placement method notch frequency of 50 Hz and notch width 10 Hz. To achieve this required the following transfer function: The transfer function can be converted into a programmable recursive algorithm: In this equation the subindex, k, means the present value, k-1 means the value in the previous instant, and so on. We now need to turn this equation into code. C coding was the automatic choice for this arithmetic-intensive processing, as programming it in assembly would have been too time consuming. Implementing the filter equations directly would be inefficient with the ADuC842, since it is not tailored for floating-point calculations. Fortunately we can just scale the coefficients (e.g. by 4096) and implement the notch code as: iNOut = (4096L*iNIn-6627L*iNIn1+4096L*iNIn2+6211L*iNOut1-3598L*iN Out2)/4096; This implements a second-order filter. Although we can calculate higher order filters, in practice it seems workable to simply cascade second-order filters. The second filter was a Butterworth pass-band filter with a 0.05-Hz low cutoff frequency and a 100-Hz high cutoff frequency. The transfer function and recursive algorithm are: This is implemented in C code by: iBOut = (1723L*iBIn-1723L*iBIn2+4745L*iBOut1-650L*iBOut2)/4096; Note that the outputs can be scaled simply by changing the coefficients of the inputs. Also note that, for efficiency (if the signals are all positive), the division by 4096 is accomplished at the end by shifting 12 right. The implementation shown in Figure 6 is for a cascade of five band-pass filters and two notch filters. The signal is scaled up by a factor of 4 in each of the first and second band-pass filters. The 12-bit right shift accomplishes the divide-by-4096. Figure 6. Essential part of C code. Note the lines, if(iAdc00>24000)iDac-= 1,, and if(iAdc00<8000)iDac += 1,, which adjust the DAC output of the ADuC842 to drive the level-shifting input of the AD620 to shift the AD620 output to a comfortable value for the MicroConverter’s ADC input. This is desirable to reduce the effects of the variable dc offsets that result from slight differences in the way the electrodes are applied to the skin. A similar technique is used to ensure that the output voltage is centered within the output range. C代码中的滤波器 获得的信号被数字滤波器处理在微转换器中。为此，我们设计了两个二阶数字信 号【infinite impulse-response (IIR) 】滤波器，基于频率为500Hz抽样，阶式滤波 器设计了支持50Hz的接口，这种设计设计方案叫零-极点布局方法，一阶的频率 为50Hz，宽度为10HZ。为了实现这个需求要用以下转换函数: 这个转换函数可以被转换为一个程序的递归算法: 在这个方程式中，,:代表当前的值，,,,:代表下一个值，以此类推。 我们现在需要变换方程式在C代码中,这个集中式算法进程中C代码是自动选择 的，这样的选择计划太费时了，直接执行这个方程式的滤波器效率太低下了，因 为它不适合浮点运算。 幸运的是，我们可以调整这个自然律的系数(例如:4096)使他变成以下形式 这是个二阶的滤波器，虽然我们可以计算出更高阶的滤波器，但是在实际生活中， 二阶的可行性更高一些。 这个二阶的滤波器的频率范围在0.0.5hz 到100Hz。转换函数和递归算法如下: 在C代码中如下: 注意，输出仅是通过改变输入的系数来改变。同时还要注意，对于效率(假如这些信息都是正确的)，这结果是,,？,向右移动,,位。 在下面图,,中展示了,个带通滤波器和,个阶式滤波器，这个信号按照每,个中第一个和第二个带通滤波器比例放大。这,,位将按照,,？,划分。 注意在这一行～和 这就需要减少变量的影响所导致作用于于皮肤的直流偏移微小的差别电极。一 个类似的技巧是用来保证输出电压是以输出范围。 Processing in Assembly Code The assembly code’s main functions are to measure the input signal at regular intervals and to ensure that the C code calculations are repeated at the required rate of 500 times per second. In the first instance, we programmed Timer0 to run continuously and generate its interrupts at 1-ms intervals. Each interrupt restarts Timer0, gets an ADC conversion result, and increments a variable, c2ms, which is used to synchronize the C code. At this stage of code development, the first few lines of C code were: while(c2ms<2); //Used in first phase. c2ms = 0; iAdc00 = iAdc0; Initially, c2ms is 0, and the C code will wait at the line while(c2ms<2);. After 1 ms, a Timer0 interrupt occurs, and c2ms is incremented to 1. After a further 1 ms, c2ms is incremented to 2. Now while(c2ms<2); is no longer satisfied, and the C code continues by resetting counter c2ms to 0 and doing the filter calculations. Thereafter, the C code shifts the results down the chain of variables representing the various delayed results ready for the next iteration of the loop. The final part of the loop is the printf(...), which sends the result to the PC for display. The processing of the data on the PC, beyond the scope of this article, can be as simple as importing it to a spreadsheet for graphical display—or as sophisticated as the designer wishes to make it. This solution produced the middle trace of Figure 5. To improve the result, the Timer0 interrupt rate was shortened to 1/32 ms, and the data was accumulated in iAdc0, to make use of multiple measurements instead of just a single measurement. At the same time, the while was changed to while(c2ms<64) so that the C code would wait for 64 measurements to be accumulated before doing each filter loop. The value in iAdc0 is saved in iAdc00 for further processing, and then iAdc0 is cleared—ready to accumulate the next 64 measurements. Figure 7 shows the assembly code. This improved solution produced the lower trace of Figure 5. Gain Signal gain is always an important consideration in an ECG signal chain. In the above-described design, it depends on a number of factors. The analog gain is set to 8×, as discussed previously. Next, a gain of 64× results from accumulating 64 measurements of this signal. Next there is a signal loss of 8× from the code iBIn = iAdc0>>3;, and finally, a gain of 4× twice from the scaling of the first two band-pass-filter equations. This results in a total gain of G = (8 × 64/8) × 4 × 4 = 1024, which is typical of analog ECG circuits. 加工汇编代码 汇编代码的主要功能是定期测量输入信号和确保C代码计算重复所需要的速度 是每秒500次。在第一个实例，我们编程的定时器0的连续运行，并产生其中 断在1毫秒的时间间隔。每个中断重新启动后的定时器 0，得到一个ADC转换 的结果，并增加一个变量，c2ms，是用于同步的代码。在这一阶段的代码开发 的，本文的几行代码是: while(c2ms<2);//在第一阶段。 c2ms=0; IAdc00=IAdc0; 最初，c2ms是0，(这时)C代码将等待行 (c2ms <2);。 1毫秒后，定时器 0发生中断和c2ms递增1。经过进一步的1毫秒，c2ms 增加为2。 而现在 (c2ms<2);不满足条件，此时C代码继续通过重置计数器c2ms为0 ，执行 ILTER计算。此后，C代码的变化结果链上的变量代表各种延迟结果，准备下一 次循环迭代。原始循环的一部分是输出(……)，其结果发送到电脑显示器。电 脑处理的数据，(如果)超出本文的范围，可以作为一个简单的导入到电子表格， 图形显示或者先进的设计者希望制作的(图表)。该解决方案产生的中间图5 的步骤。 为了提高的结果(准确率)，定时器中断率缩短到毫秒，和数据的积累01 / 32 在，利用多次测量，而不只是一个单一的测量。在与此同时，而改为iadc0 ()，因此，c2ms<64 代码将等待测量前做每个循环积累。在值保存在作进一步处C64ILTERiAdc0 理，然后清除就绪积累在未来测量。图显示了汇编代码。这iAdc00iAdc0647 种改进的解决方案产生的较低的效率图。()5 增益 信号增益始终是一个重要的考虑在心电图信号链。在上述设计，它取决于很多 因素。模拟增益设置为，以前讨论的一样。接下来，获得了64增益，这个 结果是从积累64测量 信号得到的。接下来是从代码的信号损失8从代码 ibin=iadc0>>3;，并最终，使得增益为4，两次,缩放IRST两个带通ILTER方 程。这将导致总收益=()，这是典型的模拟心电图电路。 CONCLUSION Figure 8 shows results for a subject connected in Einthoven lead I configuration. As can be seen, good results are achieved despite the simplicity of the electronic hardware used. The article demonstrates that significant improvements can be achieved with simple hardware combined with attention to software. The improvement in this example is by no means at the optimum level; it should be possible for a dedicated designer to significantly improve the results. Additional improvements could be made if code with different filter frequencies or other special characteristics were to be implemented. The code memory of the ADuC842 is flash based, allowing such customizations to be made after a product using it is manufactured—or even as the patients’ needs change. An ultimate result could be a compact, inexpensive ECG for a potentially large-volume market. REFERENCES rdWebster John G., Medical Instrumentation. Application and Design. 3 edition, Wiley, 1998. Firth J. and Errico P., “Low-Power, Low-Voltage IC Choices for ECG System Requirements,” Analog Dialogue, Volume 29, Number 3, 1995. AAMI, American National Standard, Safe Current Limits for Electromedical (ANSI/AAMI ES1-1993). Association for the Advancement of Apparatus Medical Instrumentation, 1993. AD620 Data Sheet revision F. Analog Devices, Inc., ?2003. (return to text) 1 Standard paragraph (19) from Analog Devices Terms and Conditions: USE IN LIFE SUPPORT APPLICATIONS Products sold by Analog Devices are not designed for use in life support and/or safety equipment where malfunction of the product can reasonably be expected to result in personal injury or death. Buyer uses or sells such products for use in life support and/or safety applications at Buyer’s own risk and agrees to defend, indemnify and hold harmless Analog Devices from any and all damages, claims, suits or expense resulting from such use. 结论 图8显示一个项目连接在Einthoven过我装置的结果。由此可见,尽管使用简单的 电子五金，还是取得了较好的结果。这篇文章证明显著的提高通过简单的硬件并 结合注重软件能够被取得。在这个例子中提高绝不是在最优水平; 它可能可以提 供给一个专门的设计师来显著提高的结果。额外的提高可能被创造如果用不同的 滤波器频率编码或应用其他特殊特性。ADuC842的代码的记忆是通过闪光作为基 础的，允许这样的定制被产生当一个产品使用它的制造后，甚至随着病人的需求 而改变。一个最终的结果可能是一个紧凑的,便宜的心电图，作为一个潜在的大 型市场。 参考文献 Webster John G., “Low-Power, Low-Voltage IC Choices for ECG System Requirements (医疗器械、应用和设计)”第三版，威利出版社，1998年。 Firth J. and Errico P. “Low-Power, Low-Voltage IC Choices for ECG System Requirements,(心电图系统要求的低功耗、低压IC选择)”《模拟对话》杂志，第29卷，第3期，1995年。 AAMI, 美国国家标准, Safe Current Limits for Electromedical Apparatus (电子医疗装置的安全电流限制)(ANSI/AAMI ES1-1993) 医疗器械促进协会,1993年。 AD620 Data Sheet(AD620数据表)，F.的《模拟设备》修订版，Inc，1993年。 (return to text)(回到文本) 《模拟设备》标准版第19段Terms and Conditions:(条款和条件) 使用生命支持应用程序 模拟设备产品不是设计用于生命支持和/或安全设备产品故障的地方，合理地预期将会导致人身伤害或死亡。买方使用或者销售这类产品中使用生命支持和/或安全应用在买方自己的风险并且同意防护, 保障和控制无害的模拟设备来自任何和所有索赔、诉讼、损害或费用，造成这种用途。