电气工程及其自动化专业英语 Chapter2 Electronics.ppt

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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 en

2、counter 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 shall be concer

3、ned 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,a physical quant

4、ity 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 implicitly to voltage

5、s 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 rate are the variables)can of

6、ten 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 information in two different forms

7、.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 between the two junctions varies,the magni

8、tude 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 within two discrete ranges.Such signals are

9、 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 drops below a preset value,the thermostat switch c

10、loses 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 not too cold.Section 1 IntroductionSignal-Processing Sys

11、tems 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 present the information as an output in the proper form a

12、t 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 represents the conversion of an analog signal to equivalent digital

13、 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.Section 1 IntroductionFig.2-2 Components of a signal system Section

14、 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 difference(the physical variable)to a voltage(the electrical variable).Gener

15、ally,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 to operate.Section 1 IntroductionThe output from a system can be in many forms,

16、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 size of the variable of interest)or in digital form(using a set of digital display elem

17、ents 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 input signal to another system,or to use the output as a control signal to initiate some act

18、ion.ReturnNew Words and Expressionselectronics n.电子学，电子仪器，电子设备，电子线路understatement n.轻描淡写，有节制的表达omnipresenta.无处不在的，普遍存在的electronica.电子（学）的transactionn.交易，业务 办理，处理，执行，记录digital a.数字的，数字式的，计数的espionage n.谍报，间谍活动，密探，监视 New Words and Expressionssignal-processing a.信号处理的analogn.模拟（量，装置，设备，系统）类似，类比，比拟veloc

19、ity n.速度，速率thermocouplen.热电偶discretea.离散的，不连续的，分散的household a.;n.家用的，普通的，一般用途的，家庭，家，户thermostatn.恒温器，定温器，温度自动调节器 New Words and Expressionspresetv.;a.预定，预置，（预先）调整 安装程序，给定程序的switch n.开关；v.接通或关断，转变，换接A/D=Analog-to-Digital模数转换，模数变换D/A=Digital-to-Analog数模转换，数模变换transducer n.传感器，变送器，发射器，换能器，换流器excitationn

20、.激励，激发，激磁 刺激，干扰displayv.显示，显像，表现，陈列，展览；n.显示，指示，表现 ReturnVocabulary Characteristic III除加词根和词缀外，其它构词法有：除加词根和词缀外，其它构词法有：l 合合成成法法 两个或两个以上的词结合成一个新词。专业英语中的合成词有合写式（无连字符）和分写式（有连字符）两种。hardware 硬件；software 软件；pulse-scaler 脉冲标定器。l 混混成成法法 两个词中在拼写或读音上比较适合的部分以“前一词去尾、后一词去首”的方式，加以叠合混成新词，而混成的新词兼具有两个旧词的形和义。telex=tele

21、printer+exchange 电传；transistor=transfer+resistor 晶体管。Vocabulary Characteristic IIIl 截截短短法法 删除某一词中的一个或多个音节形成新词，其词义不变。auto=automobile 汽车；lab=laboratory 实验室；amp=ampere 安培。l 缩缩略略法法 将某一词组中主要的词的第一个字母组成新词。radar=radio detecting and ranging 雷达；UPS=uninterrupted power supply 不间断电源；DC=direct current 直流电；AC 交流电

22、；CAD=computer assisted design 计算机辅助设计。Vocabulary Characteristic IIIl 转转化化法法 不通过任何词形上变化，直接转化为另一个词。在转化过程中，词性有所改变而词义则与转化前的原义仍保留若干联系。xerox 用静电复印法复印。ReturnExercises 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 con

23、trol2.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 into 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 c

24、onverts temperature difference to a .A.current B.voltage C.power D.energy Exercises I.Choose the best answer into the blank 5.A 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 a

25、ccording 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.What does the output form of a system depend on?Exercises III.Translate the fo

26、llowing into Chinese Analog electronics pertains to those systems in which the electrical voltage and electrical current are analogous to physical quantities and vary continuously.Electronic circuits that reproduce music must have voltages and currents that are proportional to the sound.A high fidel

27、ity amplifying system attempts to keep the analogy as true as possible.Analog electronic circuits are carefully designed to make the electrical voltages and currents follow the input signal.If an input signalExercises III.Translate the following into Chinese doubles in amplitude,the output voltage o

28、r current also should double;this is possible because the circuit elements are made to operate within limits that preserve the linearity.ReturnChapter 2Section 1 EndSection 2 Boolean Algebra for Digital Systemsn Textn New Words and Expressionsn Exercisesn Endn Selection of Word Meaning Section 2 Boo

29、lean Algebra for Digital SystemsIntroduction The mathematics of computers and other digital electronic devices have been developed from the decisive work of George Boole(l815l864)and many others,who expanded and improved on his work.The body of thought that is known collectively as symbolic logic es

30、tablished the principles for deriving mathematical proofs and singularly modified our understanding and the scope of mathematics.Section 2 Boolean Algebra for Digital Systems Only a portion of this powerful system is required for our use.Boole and others were interested in developing a systematic me

31、ans of deciding whether a proposition in logic or mathematics was true or false,but we shall be concerned only with the validity of the output of digital devices.True and false can be equated with one and zero,high and low,or on and off.These are the only two states of electrical voltage from a digi

32、tal element.Thus,in this remarkable algebra performed by logic gates,there are only two values,one and zero;anySection 2 Boolean Algebra for Digital Systemsalgebraic combination or manipulation can yield only these two values.Zero and one are the only symbols in binary arithmetic.The various logic g

33、ates and their interconnections can be made to perform all the essential functions required for computing and decision-making.In developing digital systems the easiest procedure is to put together conceptually the gates and connections to perform the assigned task in the most direct way.Boolean alge

34、bra is then used to reduce the complexity of the system,if possible,Section 2 Boolean Algebra for Digital Systemswhile retaining the same function.The equivalent simplified combination of gates will probably be much less expensive and less difficult to assemble.Rules of Boolean algebra for digital d

35、evicesBoolean algebra has three rules of combination,as any algebra must have:the associative,the commutative,and the distributive rules.To show the features of the algebra we use the variables A,B,C,and so on.To write relations between variables each one of which may take the value 0 or l,we use to

36、 mean “not A,”so if A=l,then =0.TheSection 2 Boolean Algebra for Digital Systemscomplement of every variable is expressed by placing a bar over the variable;the complement of =not B.Two fixed quantities also exist.The first is identity,I=l;the other is null,null=0.Boolean algebra applies to the arit

37、hmetic of three basic types of gates:an OR-gate,an AND-gate and the inverter.The symbol and the truth tables for the logic gates are shown in Fig.2-3,the truth table illustrate that the AND-gate corresponds to multiplication,the OR-gate corresponds to addition,and the inverter yield the complement o

38、f its input variable.Section 2 Boolean Algebra for Digital Systems Fig.2-3 Logic symbols and truth tables for AND,OR,NOT (a)AND；(b)OR；(c)NOTSection 2 Boolean Algebra for Digital Systems We have already found that AB=A AND Bfor the AND-gate and A+B=A OR Bfor the OR-gate.The AND,or conjunctive,algebra

39、ic form and the OR,or disjunctive,algebraic form must each obey the three rules of algebraic combination.In the equations that follow,the reader may use the two possible values 0 and l for the variables A,B,and CSection 2 Boolean Algebra for Digital Systemsto verify the correctness of each expressio

40、n.Use A=0,B=0,C=0;A=l,B=0,C=0;and so on,in each expression.The associative rules state how variables may be grouped.For AND (AB)C=A(BC)=(AC)B,and for OR (A+B)+C=A+(B+C)=(A+C)+B the rules indicate that different groupings of variables may be used without altering the validity of the algebraic express

41、ion.The commutative rules state the order of variables.For AND AB=BA Section 2 Boolean Algebra for Digital Systemsand for OR A+B=B+A the rules indicate that the operations can be grouped and expanded as shown.Before we show the remaining rules of Boolean algebra for digital devices,let us confirm th

42、e distributive rule for AND by writing the truth table,Table 2-l.We will discover soon how we knew that we could write AB+C=(A+C)(B+C),which is proved by the truth table to be a proper expansion.Section 2 Boolean Algebra for Digital SystemsTable 2-1 Truth table for the AND-distribution ruleABCAB+C=V

43、alue(A+C)(B+C)=Value0000+0 00 0 00010+1 11 1 10100+0 00 1 00110+1 11 1 11000+0 01 0 01010+1 11 1 11101+0 11 1 11111+1 11 1 1Section 2 Boolean Algebra for Digital Systems The more complex expression and its simpler form yield identical values.Because binary logic is dominated by an algebra in which a

44、 sum of ones equals one,the truth table permits us to identify the equivalence among algebraic expressions.A truth table may be used to find a simpler equivalent to a more complex relation among variables,if such an equivalent exists.We will see shortly how the reduction of complexity may be achieve

45、d in a systematic manner with truth tables and other techniques.Section 2 Boolean Algebra for Digital Systems Some additional relations in the algebra,which use identity and null,are worth nothing.Here we illustrate properties of the AND and OR operations that use the distributive rules and the fact

46、 that I is always l and null is always 0.ANDAI=A or A1=AORA+null=A A+0=AANDA =null A =0OR A+=I A+=1ANDA null=null A0=0ORA+I=I A+1=1ANDAA=AORA+A=A Section 2 Boolean Algebra for Digital Systems The relation points out an important fact,that is,that I,the identity,is the universal set.Null is called th

47、e empty set.We have considered several logical relations.For the two-value Boolean algebra of digital electronics,the choice of the technique depends upon the nature of the function whose reduction is desired.Some simple functions may be easily reduced by examining their truth table;others require t

48、he manipulation of Boolean algebra to reveal the relationship.When we consider the circuit forSection 2 Boolean Algebra for Digital Systemsadding binary numbers,we see that Boolean algebra is required to discover a simplification in that particular application.ReturnNew Words and ExpressionsBoolean

49、布尔的symbolic a.符号的，记号的，象征（性）的proofn.证明，证实，证据；v.检验，试验；a.试验过的，合乎标准的，防的singularly ad.非凡地，特殊地，奇异地，单独地logic gate 逻辑门Manipulation n.处理，计算，操作，控制，管理binaryn.;a.二进制的，二进位的，二元的，二成分的 二，双，复 New Words and Expressionsarithmeticn.算术，计算，运算；a.算术的，计算的，运算的associative a.结合的，联合的，相关的，commutative a.交换的，换向的，代替的，相互的distributiv

50、e a.分配的，分布的，个别的truth table 真值表multiplicationn.乘法，相乘 增加，增多，增殖，倍增additionn.加法 增加，附加，相加New Words and Expressionsconjunctive a.合取的，逻辑乘的 连接的，连系的disjunctive a.析取的，分离的，转折的identity n.单位，同一，完全相同，一致，恒等，身份nulln.;a.零的，空的，无 不存在的，没有的complementn.;a.补码，补数，余的，补的 补充，互补 ReturnSelection of Word Meaning 一词多类，一词多意，需词义的选择