测控技术与仪器专业英语unit6

1、测控技术与仪器专业英语unit6第一页，共43页。Unit 6 Signal Conditioning第二页，共43页。 A measuring transmitter consists of two parts: a primary element (or sensor) and a signal conditioner. The primary element uses some characteristic of its material and construction to convert the value of a measured variable into an electr

2、ical, mechanical, or fluidic signal. 译为：一个测量传感器由两部分组成：一个基本元件（传感器）和一个信号调制器。基本元件利用其材质的特性和结构将被测量转化为电的、机械的或者流体的信号。 第三页，共43页。 The output of the primary element may be a small voltage or an electrical resistance. It may be a force, a displacement, a pressure, or some other phenomenon. No matter what form

3、it takes, the primary element output depends on the value of the measured variable. 译为：基本元件的输出可能是一个小的电压或电阻。也可能是一个力、一个位移、一个压力或其他一些现象。不论它采取何种形式，基本元件的输出依赖于测得量的数值。第四页，共43页。 The output of the primary element is a measure of the variable it is sensing, but it is seldom in a form suitable for transmission

4、and use by other components in a system. 译为：基本元件的输出是对它测量的变量的度量。但是它很少采用一种便于传输或被系统中其他部分使用的形式。第五页，共43页。 Usually, a signal conditioner is required to convert the primary element output into an electrical (or pneumatic) signal suitable for use by a controller or display device. A signal conditioner prepa

5、res a signal for use by another component. The input to a signal conditioner is usually the output from a sensor (or primary element). 译为：通常，一个信号调制器被用来将基本元件的输出变换为一个便于被处理器或显示设备使用的电（或气）信号。一个信号调节器将信号准备好以备其他设备使用，信号调制器的输入通常是传感器的输出（或基本元件）。第六页，共43页。 The full-scale outputs of most sensors (passive or active

6、) are relatively small voltages, currents, resistances and capacitances. Before further analog or digital processing can take place, these outputs must be scaled or converted to useful ranges. 句中full-scale意为“满量程”，passive sensor意为“被动型传感器”，active sensor意为“主动型传感器”，scale在这里指“换算缩放，改变值的大小”。译为：绝大多数传感器（被动型或

7、主动型）的满量程输出都是比较小的电压、电流、电阻和电容。在进行进一步模拟或数字信号处理之前，这些输出必须要换算缩放或转换到可用的范围。第七页，共43页。 The standard transmission signals are a 4 to 20mA electric current or a 3 to 15psi pneumatic pressure. For example, a thermocouple（热电偶）(T/C) is a primary element that converts temperature into a small voltage.A signal condi

8、tioner converts the millivolt output of the thermocouple into a 4 to 20mA electric current. A T/C temperature transmitter includes both the thermocouple and the signal conditioner. psi为压力的单位，pounds per square inch，磅/平方英寸。pneumatic pressure意为“气压”. 译为：标准的传输信号是一个4至20毫安电流或一个一个3至15磅/平方英寸气压。例如，热电偶是一种将温度转化

9、为小电压的基本元件。一个信号调制器将热电偶的毫伏输出转化为4至20毫安的电流，一个热电偶温度变送器同时包含热电偶和信号调制器。第八页，共43页。 Signal conditioning circuits perform the necessary amplification, level translation, impedance transformation, linearization and filtering. The characteristics of and error in the sensor output determine the type of signal cond

10、itioning circuits needed. 译为：信号处理电路实现必要的信号放大、电平变换、阻抗变换、线性化和滤波。传感器输出的特征及其误差决定需要哪种信号调制回路。 第九页，共43页。If the sensor output is not conditioned properly, factors such as sensitivity, voltage and current levels, linearity（线性度，线性）, impedances, gain, offset, drift, time constants, maximum electrical ratings（最

11、大额定电功率）, stray impedances（杂散阻抗，寄生阻抗）and other important considerations can impact the overall performance of the sensor. As a result, the overall system will suffer, particularly when high resolution, precision or very low level measurements are involved. 译为：如果传感器的输出没有被正确的调制，诸如灵敏度、电压和电流电平、线性度、阻抗、增益、

12、补偿、漂移、时间常数、最大额定电功率、寄生阻抗和其他重要的因素能够影响传感器的整体表现。其结果是整个系统将受到影响，特别是当涉及高清晰度，准确度或很差水平的测量时。第十页，共43页。 Care must be taken when designing signal generation and conditioning circuits to ensure that the sensor is the least accurate component of the system. If surrounding circuitry adds noise or degrades accuracy,

13、 the accuracy of the sensor output is compromised. 译为：设计信号发生器和调制回路时一定要警惕以保证传感器是系统中准确度最低的部件，如果周围回路有附加噪声或降低了准确度，传感器输出的准确度将受影响。 第十一页，共43页。 The following are some of the tasks performed by a signal conditioner: 以下是一个信号调制器执行的操作：（1）Isolation and impedance conversion;隔离和阻抗变换（2）Amplification and analog-to-a

14、nalog conversion; 放大和模-模转换（3）Noise reduction (filtering); 降噪（滤波）（4）Linearization; 线性化（5）Data sampling; 数据采样（6）Digital-to-Analog conversion; 数-模转换（7）Analog-to-Digital conversion. 模-数转换第十二页，共43页。Voltage output Three types of input topologies exist for the signal conditioning of voltage output sensors:

15、 differential, single-ended and pseudo-differential. The type of signal conditioning input is typically matched to the output structure and precision requirements of the sensor . 句中differential有“微分”和“差分”之意，这里指信号处理的方式，意为“差动”。译为：电压输出传感器的信号处理有3种输入拓扑方式：差动方式、单端方式和伪差分方式。信号调制输入的类型要符合特定的输出结构和传感器的准确性要求。第十三页，

16、共43页。 A differential device rejects input signals common to the balanced input pair (+ and -) while accepting the difference between the input signals, specified as the Common-Mode Rejection Ratio (CMRR). The device is designed so that the noise common to both inputs is rejected while the signal of

17、interest is not. 句中balanced input意为“对称输入”，Common-Mode Rejection Ratio (CMRR)意为“共模抑制比”。译为：差动装置在接收两输入端口的差分信号时，抑制这两个对称输入端口（+和-）的共模输入信号，这称为共模抑制比CMRR。这个装置被这样设计两个输入共有的噪声被抑制而所需要的信号不被抑制。第十四页，共43页。 Much like digital differential input signals such as LVDS, the analog signals may be inverted to a double dynam

18、ic range as is common with differential output devices. 译为：和数字差分输入信号如低压差分信号很类似 ，模拟信号可以倒置成一个双重动态范围和差分输出设备的输出一样。第十五页，共43页。This type of input topology（拓扑，拓扑结构，布局，拓扑学）is used when maximum noise rejection is required and the sensor measurement is not tied to ground, as with the Wheatstone bridge（惠斯顿电桥）co

19、nfiguration. For remote sensor applications, shielded twisted pair cables should be used in order to maintain signal balance and share a common ground reference. 句中twisted pair cables意为“双绞线”。译为：这种输入拓扑形式在需要最大噪声抑制和传感器测量装置没有接地时使用，后者和惠斯顿电桥的结构相类似。对远程传感器应用，应该使用屏蔽双绞线以保持信号的平衡和共地。第十六页，共43页。 In contrast, a si

20、ngle-ended (SE) device has a single signal input. The board designer must ensure a common ground between the device and its input, which is the sensor circuitry in this case. Therefore, SE devices are generally placed in close proximity to one another to mitigate（减轻，缓和）the possibility of reference d

21、ifferences between the devices. 译为：相反地，一个单端设备只有一个信号输入端。面板设计员必须保证设备和其输入之间有共同之处，传感器回路就是这种情况。因此，单端设备通常彼此紧密排列以减少设备间相互参照引起的不同的可能。 第十七页，共43页。In general, SE devices are used for conditioning larger signals and are not tied directly to small signal sensors. Although SE devices have lower CMRRs and introduce

22、 greater DC offsets（偏移，偏置）, they are less costly. For remote sensor applications, coaxial（同轴的，共轴的）cables are sufficient for shielding the signal conductor and sharing common ground references. 译为：通常情况下，单端设备用来调制较大的信号而且不直接连接在小的信号传感器上。尽管单端设备有较低的共模抑制比和较大的直流抵消，它们更便宜。对长距离传感器设备而言，同轴电缆足够用于信号传导和共地。第十八页，共43页。

23、 Finally, a pseudo-differential input topology is a hybrid of the two. Its DC offset performance approaches that of a differential device, but its CMRR is closer to a SE device. This type of device is used in cost-sensitive designs with DC sensors where high frequency variations from noise can be re

24、moved at the end of the signal chain or through digital processing. 句中DC是direct current的缩写，意为“直流电”。译为：最终，一个拟微分输入拓扑是两种的混合，它的直流抵消能力接近与差分装置，但它的共模抑制比更接近单端设备。这种类型的装置用于有直流传感器的代价敏感的设计中，这种装置能在信号链的终端或通过数字信号处理去除噪声的高频变化。第十九页，共43页。Amplification For circuits with small voltage outputs, a precision amplifier gain

25、 stage is needed. As sensor outputs are typically processed by analog-to-digital converters, the sensor output needs to be amplified so that it can take advantage of the full-scale input range of the desired ADC (analog-to-digital converters ). 译为：对小电压输出的电路，一个准确的放大增益级是需要的。因为传感器的输出被模-数转换装置按特定方式处理，传感器

26、输出需要被放大以此使它能够利用要求的模数转换器的宽频输入的优势。第二十页，共43页。For very low-level input signals, multiple levels of amplification and high gains are sometimes required. Because of the operational amplifiers（运算放大器）architecture, input offset voltage and input bias（偏差，偏移，偏置）current can add error to the amplifiers input. 译为

27、：对于低电平输入信号，有时需要多级放大和高增益。因为运算放大器的结构，输入电压偏移和输入电流偏移会增加放大器的输入的误差。第二十一页，共43页。The effects of input offset voltages and input bias currents are shown in Figure 6.1. As previously stated, high gains also amplify input offset voltages, potentially adding large amounts of error to the amplified sensor signal.

28、 译为：输入电压偏移和输入电流偏移的作用如图6.1.正如之前说过的，高增益也会放大输入电压偏移，可能给放大的信号增加大量误差。Figure 6.1 Voltage output sensing第二十二页，共43页。 Non-ideal features of operational amplifiers： 运算放大器的非理想特性： Voltage Offset(电压偏移): Input offset voltage results primarily from the inherent mismatch of an operational amplifiers input transistor

29、s. 译为：电压偏移：输入电压偏移主要由运算放大器的输入晶体管固有的不匹配产生。第二十三页，共43页。Input Bias Current(输入偏移电流): While an ideal operational amplifier has zero current flowing into the input transistors, a small amount of current does flow into or out of the input transistors.译为： 输入偏移电流：当一个理想运算放大器没有电流流入输入晶体管，一小部分电流流入或流出输入晶体管。 Common

30、Mode Rejection(共模抑制): In a single-ended input operational amplifier, noise on the input signals is amplified with the gain of a circuit. In a differential input stage, noise common to both inputs is rejected, passing only the signal of interest.译为：共模抑制：在一个单端输入运算放大器中，输入信号中的噪声在增益的回路中放大。在差分输入级，两个输入端共同的

31、噪声被抑制，仅允许需要的信号通过。第二十四页，共43页。 To avoid large offset voltages with very low-level voltage outputs, an instrumentation amplifier should be used. Instrumentation amplifiers are designed using three discrete operational amplifiers, with non-inverting operational amplifiers used as input buffers to each d

32、ifferential input. 译为：为避免低电平输出中的大的电压偏移，需要使用仪器放大器。仪器放大器由3个分离的运算放大器设计而成，其中，非反相运算放大器用于每个不同输入信号的输入缓冲。第二十五页，共43页。This configuration is typically integrated into a single device. Many sensors (with differential output) connect directly to the instrumentation amplifier. In many cases, the instrumentation a

33、mplifier gain is set relatively low and then followed up by a high gain operational amplifier. Instrumentation amplifiers, shown to the right in Figure 6.2, have very low input offset voltages, low input bias currents and high common mode rejection, reducing error in the initial gain stage. 译为：这种结构合

34、成为一个单独的装置。许多传感器（与差分输出）直接与仪器放大器相连。在许多情况中，仪器放大器的增益设置的相对低并且后面跟随一个高增益的运算放大器。仪器放大器，显示在图6.2的右侧，有很低的输入电压偏移和输入电流偏移，以及高共模抑制比，降低起始增益环节的误差。第二十六页，共43页。 Following the initial gain stage, a programmable gain amplifier can be used to further amplify the signal as needed. A programmable gain amplifier can be digita

35、lly programmed to ensure that the full scale sensor output matches the input voltage range of the analog-to-digital converter. 译为：在起始增益环节之后的是一个可编程增益放大器，它可以用来根据需要进一步放大信号。一个可编程起始增益放大器可以进行数字化编程以确保传感器输出的满量程与模数变换器的电压输入范围相匹配。第二十七页，共43页。Figure 6.2 Instrumentation amplifier offset voltages第二十八页，共43页。Noise S

36、ensor signals running long distances over wire and cable essentially become antennas, picking up electrical and magnetic interference from many RF sources. Ground loops（地回路，接地环路）on single-ended signals can also significantly raise/lower the noise potential of a sensor signal with respect to the sign

37、al conditioning circuits. 译为：传感器信号经长距离传输，必然变得像天线一样，容易受到许多射频源的电磁干扰。单端信号的接地回路也能够显著的提高/降低传感器信号关于信号调制回路产生的噪声势。第二十九页，共43页。Using balanced (differential) signals, sensible grounding strategies, twisted pair wires and appropriate filtering at the amplifier stage can significantly improve noise immunity(抗噪声度

38、). 译为：使用平衡（差分）信号，合理的接地策略，双绞线和放大级中适当的过滤可以显著提高抗噪声度。第三十页，共43页。Isolation Some sensor environments and conditioning circuits have significantly different potentials and can be subject to very high-voltage transients on the sensor signal path. These situations can potentially damage low-voltage data conve

39、rsion and processing circuits, creating the need for an isolation circuit to protect the circuitry. The sensor half of the system is said to be isolated from the rest of the system. 句中high-voltage transient意为“瞬时高压”。译为：有些传感器环境和信号处理电路有明显不同的电位，在传感器信号传输路径中，容易受到瞬时高压的影响。这些情况可能破坏低电平数据转换和运算电路，由此需要一个隔离电路来保护电

40、路。系统内一半的传感器因此需从系统其余部分隔离出来。第三十一页，共43页。 Isolation circuits are created by taking advantage of electric and magnetic field properties in structures such as transformers, capacitors, photoelectric devices and RF signal propagation to transmit data across an interface without a physical connection. Isola

41、tion amplifiers have the isolation barrier necessary to protect downstream circuits integrated directly into the device. Transformer, capacitor, optical and RF isolation amplifiers all have differing accuracy, linearity and bandwidths（带宽）. 译为：隔离电路利用电磁原理的构件制成。如变压器、电容器、光电元件和RF信号发射元件，通过没有物理连接的界面来传送数据。隔

42、离放大器有隔离栅的需要以保护下游直接与设备集成的电路。变压器，电容器，光学和射频隔离放大器都有不同的准确率，线性度和带宽。第三十二页，共43页。Filtering At some point in the signal chain, generally just before digitization, the signal is filtered to attenuate unwanted cross-talk（声道串扰，串音）components such as 60Hz hum （交流声；干扰；发嗡嗡声）, switching transients（开关瞬态；操作瞬变现象）, RF in

43、terference as well as aliasing artifacts（混叠伪像）such as wideband noise. Analog signal filtering can be broken into two basic types: passive and active. 译为：在信号链的某些点，通常是在数字化之前，信号被过滤以减弱不需要的串音成分如60hz的交流声，开关瞬态，射频干涉混叠伪像例如宽频噪声。模拟信号的过滤可以分为两种基本类型：被动型和主动型。第三十三页，共43页。Passive analog filters use discrete component

44、s such as capacitors, inductors and resistors. Active analog filters use discrete components in conjunction with operational amplifiers for a more precise filter design. 句中Passive analog filters指“被动模拟滤波器”，也称无源滤波器。Active analog filters指“主动模拟滤波器”，也称有源滤波器。译为：被动模拟滤波器由电容、电感和电阻这样的独立元件构成。主动模拟滤波器将这些独立元件连接在运

45、算放大器上，得到更高的设计精度。第三十四页，共43页。 Filters, whether active or passive, can be broken down into three basic functional areas: low-pass filters, high-pass filters and bandpass filters. Low-pass filters (LPFs)（低通滤波器）only allow electrical signals under a determined frequency to pass through, often called the c

46、ut-off frequency. High-pass filters (HPFs)（高通滤波器）allow electrical signals to pass though that is above the cut-off frequency. 译为：滤波器，不论主动式或被动式，可以分成三种基本功能类型：低通滤波器，高通滤波器和带通滤波器。低通滤波器仅允许低于一定频率，通常成为截断频率的电信号通过。高通滤波器允许频率高于阶段频率的电信号通过。第三十五页，共43页。Bandpass filters（带通滤波器）are a combination of an LPF and an HPF.

47、They allow electrical signals to pass through that are above a lower cut-off frequency and below a higher cut-off frequency. Designers have to take care when choosing the appropriate type and functional area to achieve optimal circuit performance. 译为：带通滤波器是低通滤波器和高通滤波器的混合。他们允许高于一个较低截断频率且低于一个较高截断频率的电信

48、号通过。设计人员应注意选择合适类型和功能的滤波器以达到理想的电路性能。第三十六页，共43页。Analog-to-analog conversion Some primary elements convert changes in the measured variable into small changes in resistance. Strain gages（应变仪）and resistance temperature detectors (RTDs) are two examples. A bridge circuit is often used to convert the chan

49、ge in resistance into a small change in voltage. This small voltage is then amplified and converted to an electric current signal suitable for use by the controller。 注意句中changes强调转换的不是被测量本身，而是被测量的“变化量”。译为：一些基本元件将被测量的变化量转换成电阻的很小的变化量。应变仪和电阻温度检查器是两个例子。一个桥路常被用来将电阻的变化转换为电压的微小变化。这个小的电压随后本放大并转化为一个适合被控制器使用的

50、电流信号。第三十七页，共43页。Offset voltage correction Sometimes, the output of either a sensor or an amplifier gain stage adds a DC offset to the sensor signal. If the offset is not removed, the amplified sensor output may saturate（浸透，充斥）the input range of the ADC, causing loss of sensor data. A digital-to-analog converter can be used to remove sensor offset or operational amplifier offset voltages. 译为：往往，无论是传感器或是放大增益级的的输出给传感器信号增加直流偏移。如果偏移没有被消除，被放大的传感器输出也许会溢出模数转换器的输入范围，造成传感数据的流失。一个数模转换器可以用来消除传感器偏移或运算放大器电压偏移。第三十八页，共43页。Current output If the output of