電氣工程與自動化專業(yè)英語PPT課件21

1、Chapter 2ElectronicsSection 1 Introductionn Textn New Words and Expressionsn Exercisesn Endn Vocabulary Characteristic IIISection 1 Introduction To say that we live in an age of electronics is an understatement. From the omnipresent integrated circuit to the equally omnipresent digital computer, we

2、encounter electronic devices and systems on a daily basis. In every aspect of our increasingly technological society whether it is science, engineering, medicine, music, maintenance, or even espionagethe role of electronics is large, and it is growing. In general, all of the tasks with which we shal

3、l be concerned can be classified as signal-processingSection 1 Introductiontasks. Let us explore the meaning of this term. Signal A signal is any physical variable whose magnitude or variation with time contains information. This information might involve speech and music, as in radio broadcasting,

4、a physical quantity such as the temperature of the air in a room, or numerical data, such as the record of stock market transactions. The physical variables that can carry information in an electrical system are voltage and current. When we speak of signals, therefore, Section 1 Introductionwe refer

5、 implicitly to voltages or currents. However, most of the concepts we discuss can be applied directly to systems with different information-carrying variables. Thus, the behavior of a mechanical system (in which force and velocity are the variables) or a hydraulic system (in which pressure and flow

6、rate are the variables) can often be modeled or represented by an equivalent electrical system. An understanding of the behavior of electrical systems, therefore, provides a basis for understanding a much broader range of phenomena. Section 1 IntroductionAnalog and Digital signalsA signal can carry

7、information in two different forms. In an analog signal the continuous variation of the voltage or current with time carries the information. An example, in Fig.2-l, is the voltage produced by a thermocouple pair when the two junctions are at different temperatures. As the temperature difference bet

8、ween the two junctions varies, the magnitude of the voltage across the thermocouple pair also varies. The voltage thus provides an analog representation of the temperature difference. Section 1 IntroductionThe other kind of signal is a digital signal. A digital signal is one that can take on values

9、within two discrete ranges. Such signals are used to represent ON-OFF or YES-NO information. An ordinary household thermostat delivers a digital signal to Fig.2-1(a) An example of an analog signal; (b) Voltage-time characteristic Section 1 Introductioncontrol the furnace. When the room temperature d

10、rops below a preset value, the thermostat switch closes turning on the furnace. Once the room temperature rises high enough, the switch opens turning off the furnace. The current through the switch provides a digital representation of the temperature variation: ON equals too cold while OFF equals no

11、t too cold. Section 1 IntroductionSignal-Processing Systems A signal-processing system is an interconnection of components and devices that can accept an input signal or a group of input signals, operate on the signals in some fashion either to extract or improve the quality of the information, and

12、present the information as an output in the proper form at the proper time. Fig.2-2 illustrates the components in such a system. The central circles represent the two types of signal processing (digital and analog), while theSection 1 Introductionblock between the two signal- processing blocks repre

13、sents the conversion of an analog signal to equivalent digital form (A/D=Analog-to-Digital) and the reverse conversion of a digital signal to the corresponding analog form (D/A=Digital-to-Analog). The remaining blocks involve inputs and outputs getting signals into and out of the processing system.

14、Section 1 IntroductionFig.2-2 Components of a signal system Section 1 Introduction Many electrical signals derived from physical systems are obtained from devices called transducers. We have already encountered an example of an analog transducer, the thermocouple pair. It converts temperature differ

15、ence (the physical variable) to a voltage (the electrical variable). Generally, a transducer is a device that converts a physical or mechanical variable to an equivalent voltage or current signal. Unlike the thermocouple example, however, most transducers require some form of electrical excitation t

16、o operate. Section 1 IntroductionThe output from a system can be in many forms, depending on the use to be made of the information contained in the input signals. One can seek to display the information, either in analog form (using a meter, for example, in which the needle position indicates the si

17、ze of the variable of interest) or in digital form (using a set of digital display elements that are lit up with a number corresponding to the variable of interest). Other possibilities are to convert the output to sound energy (with a loudspeaker), or to use the output asSection 1 Introductionan in

18、put signal to another system, or to use the output as a control signal to initiate some action. New Words and Expressionselectronics n. 電子學(xué)，電子儀器，電子設(shè)備，電子線路understatement n. 輕描淡寫，有節(jié)制的表達omnipresenta. 無處不在的，普遍存在的electronica. 電子（學(xué)）的transactionn. 交易，業(yè)務(wù) 辦理，處理，執(zhí)行，記錄digital a. 數(shù)字的，數(shù)字式的，計數(shù)的espionage n. 諜報，間諜活

19、動，密探，監(jiān)視 New Words and Expressionssignal-processing a. 信號處理的analogn. 模擬（量，裝置，設(shè)備，系統(tǒng)） 類似，類比，比擬velocity n. 速度，速率thermocouplen. 熱電偶discretea. 離散的，不連續(xù)的，分散的household a.; n. 家用的，普通的，一般用途的，家庭，家，戶thermostatn. 恒溫器，定溫器，溫度自動調(diào)節(jié)器 New Words and Expressionspresetv.; a. 預(yù)定，預(yù)置，（預(yù)先）調(diào)整 安裝程序，給定程序的switch n. 開關(guān)； v. 接通或關(guān)斷，轉(zhuǎn)

20、變，換接A/D = Analog-to-Digital模數(shù)轉(zhuǎn)換，模數(shù)變換D/A = Digital-to-Analog數(shù)模轉(zhuǎn)換，數(shù)模變換transducer n. 傳感器，變送器，發(fā)射器，換能器，換流器excitationn. 激勵，激發(fā)，激磁 刺激，干擾displayv. 顯示，顯像，表現(xiàn)，陳列， 展覽；n. 顯示，指示，表現(xiàn) Vocabulary Characteristic III除加詞根和詞綴外，其它構(gòu)詞法有：除加詞根和詞綴外，其它構(gòu)詞法有：l 合成法合成法 兩個或兩個以上的詞結(jié)合成一個新詞。專業(yè)英語中的合成詞有合寫式（無連字符）和分寫式（有連字符）兩種。 hardware 硬件；so

21、ftware 軟件； pulse-scaler 脈沖標(biāo)定器。 l 混成法混成法 兩個詞中在拼寫或讀音上比較適合的部分以“前一詞去尾、后一詞去首”的方式，加以疊合混成新詞，而混成的新詞兼具有兩個舊詞的形和義。 telex = teleprinter + exchange 電傳； transistor = transfer + resistor 晶體管。 Vocabulary Characteristic IIIl 截短法截短法 刪除某一詞中的一個或多個音節(jié)形成新詞，其詞義不變。 auto = automobile 汽車； lab = laboratory 實驗室； amp = ampere 安培

22、。 l 縮略法縮略法 將某一詞組中主要的詞的第一個字母組成新詞。 radar = radio detecting and ranging 雷達； UPS = uninterrupted power supply 不間斷電源； DC = direct current 直流電； AC 交流電； CAD = computer assisted design 計算機輔助設(shè)計。 Vocabulary Characteristic IIIl 轉(zhuǎn)化法轉(zhuǎn)化法 不通過任何詞形上變化，直接轉(zhuǎn)化為另一個詞。在轉(zhuǎn)化過程中，詞性有所改變而詞義則與轉(zhuǎn)化前的原義仍保留若干聯(lián)系。 xerox 用靜電復(fù)印法復(fù)印。 Exerci

23、ses I. Choose the best answer into the blank 1. The voltage produced by a thermocouple pair is signal. A. a digital B. an analog C. a discrete D. a control2. ON-OFF information can be represented by signal. A. a digital B. an analog C. a continuous D. a control Exercises I. Choose the best answer in

24、to the blank 3. A device that can convert an analog signal to the corresponding digital form is called for short. A. A/DB. D/A C. D/DD. A/A4. The thermocouple pair converts temperature difference to a . A. current B. voltage C. power D. energy Exercises I. Choose the best answer into the blank 5. A

25、D/A is a device that can convert a digital signal to the equivalent . A. digital formB. numerical form C. binary form D. analog formExercises II. Answer the following questions according to the text 1. What is a signal?2. Which forms can a signal carry information in?3. What basic components does a signal-processing system consist of ?4. What role does a transducer play in a signal-processing system?5. Wh