单片机防酒后驾驶控制系统相关英文及翻译

1、.1英文原文Data ConvertersThe current upsurge in the use of digital processing techniques ,brought about by developments in very large scale integration, has forced the role of the interface elements between analog and digital systems to the forefront of attention. Data converters are these interface ele

2、ments. Although they were once regarded by electronics engineers as e*pensive, rather specialized pieces of equipment , they are now monplace . They are available as self-contained functional units, in both modular and low cost integrated circuit from . No one with an interest in modern electronic i

3、nstrumentation techniques can afford tube without a sound knowledge and understanding of the operation, capabilities and limitations of these devices.USEFULNESS OF CONVERTERSIn many of the real world systems studied by scientists and engineers the system parameters are continuously changing quantiti

4、es (analog variables)and when electronic measurement techniques are used data is derived in analog form as the electrical output signal of a transducer .It is perfectly possible to process ,manipulate and store analog data using a purely analog electronic system : negative feedback techniques can ma

5、ke analog systems perform very precisely. 1However , the accuracy of a purely analog system is often not usable because of the difficulty of rending , recording and interpreting analog data with high accuracy . Also , when large amounts of analog data are involved the task of analysis and storage as

6、sumes mammoth proportions .Digital electronic systems can be made to process rapidly and accurately , to manipulate and to store large amounts of data . The advent of low cost digital microprocessor systems has drastically reduced the cost of implementing digital data processing . Microprocessors ma

7、ke it possible to e*tend the use of electronic digital techniques into areas where they were formerly not considered practicable because of economic considerations . However ,m digital circuits only operate on digital data the scientist who wishes to avail himself of the power of digital techniques

8、must first transform his analog data into digital form . A system called an analog to digital converter,ADC ,is used to perform this function and a system called a digital to analog converter ,DAC ,performs the opposite type of conversion , transforming digital data into analog from . ADCs and DACs

9、provide the essential interface which is required between analog and digital systems . The ADC allows a digital system to take in information from an outside analog system-the digital system can then rapidly process and analyses this information . The DAC allows the results of such analyses to be mu

10、nicated back to the analog system perhaps to modify or control its action .ADC and DAC systems are not new but until paratively recently they were e*pensive to implement and have consequently been regarded as rather specialized pieces of equipment . The advent of low cost monolithic IC converter dev

11、ices has changed this position: they make awide range of versatile signal processing techniques economically available to the measurement scientist who is prepared to invest some of his time in familiarizing himself with the latest devices and their capabilities . The material which follows is inten

12、ded to serve as a first step in such a familiarisation e*ercise.Rather than attempt a survey of available converter devices , which , in a fastchanging area such as this ,would be doomed to obsolescence even before it was pleted , we concentrate on the principles underlying the most popular conversi

13、on techniques . Specific IC devices are mentioned , but only as a means of relating the discussion to practical circuits which you can e*perimentally evaluate for yourself-there is no substitute for hands on practical e*perience in this type of learning e*ercise . However , it should not be assumed

14、that the devices referred to are he only ones , nor indeed the best ones available (from a cost /performance standpoint). The choice of the best converter for a specific application can only be made from athorough study of the manufacturers latest product guides .ANALOG TO DIGITAL CONVERSION TECHNIQ

15、USparison Of A/D Conversion TechniquesA brief summary is now given in which the main characteristics of devices which use the various conversion techniques that have been discussed will be pared . There are normally there dominant factors which govern the choice of the A/D converter to be used in an

16、 application : speed , accuracy and cost . It is convenient to pare the different techniques in relation to these three factors .Speed limitations are inherent in the particular techniques but arrange of speeds can be e*pected for different converter devices using the same conversion technique . A s

17、peed/accuracy design promise is inherent in all the conversion techniques . Increase accuracy is obtained at the e*pense of a reduction in conversion speed . In general , cost is directly related to speed and accuracy , but the cost of a converter device(indeed of any device) , is greatly influenced

18、 by market factors which might be quit unrelated to the performance of the device . The bigger the market is , the more firms there will be attempting to get a slice of it , and petition brings down the cost .As far as inherent speed imitations are concerned the techniques discussed in this chapter

19、in order of decreasing speed (increase in conversion time )are : parallel conversion , successive appro*imation conversion , tracking conversion and integrating conversion .If sheer conversion speed is a dominating factor in an application , the designer will have to choose a converter which uses th

20、e parallel conversion technique . At the time of writing there are not many ultra-fast converters on the market and they tend to be e*pensive , particularly the higher resolution devices . Some firms which make very fast converters are TRW LSI Products , Datel-Intersil, puter Labs and Motorola . Ava

21、ilable parallel converters achieve an 8-bit conversion time of the order of 30ns . Applications in which conversion time must be very short are increasing for e*ample, radar , digital TV and fast transient event recorders . 11,12 No doubt this growing range of applications will interest more manufac

22、turers in very high speed converters and will result in a greater number of less costly devices appearing on the market.In converters which use the successive appro*imation technique conversion time is reated to the number of bits(to the resolution ) . The fastest successive appro*imation converters

23、 currently available are 8-bit devices which have a conversion time of the order of 0.8us. General purpose 8-bit devices may be e*pected to have conversion time of the order of 30us . High resolution 16-bit successive appro*imation converter modules have conversion times of the order of 400us .Succe

24、ssive appro*imation is probably the most widely used technique in the A/D converters which are currently available ; there are a large number of manufacturers making many different successive appro*imation devices . The successive appro*imation technique has more possible sources of error than the s

25、lower integrating techniques . The highest performance successive appro*imation converters are usually the discrete ponent modular type . Costs rise steeply if the application calls for state-of-the-art speed and accuracy . Successive appro*imation converters must be preceded by a sample/hold module

26、 when they are used to digitize rapidly changing analog signals(see section 5.3 ).Tracking converters , unlike successive appro*imation types , do not require an input sample/hold . Although they use simpler digital logic circuitry than successive appro*imation tyes they are subject to similar error

27、s , but do not have the speed of a successive appro*imation converter preceded by a sample/hold(see section 5.8.5). There are paratively few tracking or counting-type converters on the market pared with successive appro*imation and integrating types.Integrating converters are the slowest type but th

28、ey are capable of very high accuracy . Conversion times of currently available integrating types range from 0.3 ms for a fast 8-bit converter to 250 ms for a slow 16-bit one .The integrating technique has the advantage of averaging-out noise ponents of the analog input signal whose frequencies are h

29、igher than the inverse of the integration period . Integrating converters do not require sample/holds. If the application is one in which the analog signals are slowly varying an integrating converter will provide the greatest accuracy for the least cost . Integrating converters are available from a

30、 large number of manufacturers .SUCCESSIVE APPRO*IMATION A/D CONVERTERThe successive appro*imation A/D conversion technique provides a more rapid conversion than the other two feedback techniques . The digital logic circuitry used in this technique instead of incrementing the D/A converter output on

31、e LSB at time , performs a series of trial conversions, In the first trial the control logic applies the MSB to the D/A converter and the analog output of the D/A converter (1/2 full scale) is pared with the analog input signal by the parator . If the DACs output is less than the analog input the MS

32、B is retained ; if the DACs output is greater than the analog input the MSB is switched OFF. The control logic then goes on to apply the nest MSB which is retained or discarded depending on the result of the parison between the DACs output and analog input . The process of trying the addition of suc

33、cessively smaller bits and retaining or discarding them depending on the result of the trial , goes on until the LSB is reached ; the conversion is then plete .A simplifiedrepresentation of the timing sequence which occurs in a typical 4-bit successive appro*imation A/D conversion is shown in figure

34、 .DIGITAL TO ANALOG CONVERTER APPLICATIONSUntil quite recently there has tended to be a clear distinction between analog and digital electronic systems . Functional operations such as amplification , wave-form generation , filtering , modulation and demodulation , etc ., have traditionally been rega

35、rded as purely analog operations ; In many cases the implementation of such functions has been founded on operational amplifier based circuitry .1 Logical operations involved in process control and mathematical operations per-formed on abstract digital numbers have been the main area of application

36、for digital electronic systems . Digital systems are founded on circuitry using gates , flip flops , counters , shift registers ,etc .One of the main reasons for the divisions of electronic systems between analog and digital has been the high cost of data converters . data converters are the essenti

37、al interface ponents which allow analog and digital devices to word together . The ine*pensive monolithic data converters which are now available make it economically viable to bine analog and digital devices . Such a converters permit a precise digital control to be added to analog functional appli

38、cations ; they also allow many of the traditionally analog functional operations to be performed with circuitry based on digital devices . This chapter gives e*amples of some of the many analog/digital applications that are possible with the use of data converters .中文翻译数据转换器超大规模集成电路的开展，掀起了使用数字处理技术的高

39、潮，促进人们必须重视模拟和数字系统间接口部件的作用。数据转换器就是这种接口部件。他们虽曾被工程师一度认为昂贵而专门转化的装置，而现在已经平凡无奇。他们可作为整体的功能单元，以模块形式或廉价的集成电路形式提供。对现代电子仪器技术感兴趣的人，都应该熟悉或了解这些器件的操作、能力和围。转换器的用途在科学家和工程师所研究的许多现实系统中，系统的参数是连续变化的量。在采用电子测量技术的情况下，数据是以传感器电输出信号那样的模拟形式取得的。要对模拟数据进展处理、操作和存贮，是用纯模拟的电子系统是完全可能的：负反响技术能够使模拟系统十分准确的工作。然而，由于高精度的模拟数据难以读出、记录和解译，纯模拟系统的

40、精度常常不便于使用。而且当涉及到大量模拟数据的时候，数据的分析与存贮要花费极大的工作量。数字的电子系统可以做到处理快速而准确，且操作和存贮的数据量可很大，廉价的数字为处理器系统的出现以急剧地降低了实施数字数据处理的费用。以前由于经济上的缘故，认为不能推广应用电子数字技术的领域，微处理器以使之成为可能。不过，数字电路只能操作数字的数据，科学家想要利用数字技术的能力必须首先将模拟的数据转换成为数字的形式。所谓“模数转换器ADC的系统可以实现上述功能，而称为“数模转换器DAC的系统则实现相反的转换，即将数字数据转换为模拟形式。ADC和DAC为模拟系统与数字系统之间提供了必要的根本接口。ADC可是数字

41、系统从外界的模拟系统取得信息，数字系统就能很快处理与分析这些信息。DAC可将这种分析结果回送给模拟系统，调整或控制其动作。ADC和DAC并非新器件，只是不久以前他们的价格颇为昂贵，一直被认为是设备中相当专门化的局部。廉价的单片IC集成电路转换器件的出现改变了这种情况：他们可以使通用围较广的信号处理技术为量测科学家经济地所利用，只要他们愿意花费一些时间去熟悉最新的器件及其功能。转换器的开展是如此之快，往往在其打到完备以前就陷于旧。我们与其介绍一些常用的器件，还不如着重于一般通用的转换技术的原理。具体的IC器件也要有所涉及，但只是便于联系实际线路进展讨论。在这类学习的训练中“亲手实践是最好的方法。

42、要为特定的应用选择“最好的转换器，只有全面了解制造厂的最新产品指南以后才能做到。模数转换技术A/D转换技术的比较对各有关器件的主要性能做出比较。选用A/D转换器一般要考虑三个主要因素：速度、精度与价格,用这三个因素就便于对不同的转换方法进展比较。对于*一转换方法，有着其固有的速度限制；但采用同一种转换方法时，不同的转换期间也有可能有不同的速度围。各种转换方法在设计上均存在着速度/精度的权衡。要提高精度，势必降低转换速度。一般来说，价格与速度和精度直接相关，但是转换器件的价格实际是任何器件的价格，很大程度又受市场因素的影响。而市场因素也可能与器件性能无多大关系。市场越大，越有许多厂家要去瓜分，竞争就是价格下降。就固有的速度限制而论，假设以速度减慢转换时间增加的次序对各种方法做一排列，应为：并行转换、逐次逼近型转换、跟踪型转换和积分型转换。假设应用中高速转换速度是主要因素，则设计这就只有选择采用并行转换方法的器件。到编写时为止，市场上尚没有许多超高速的器件，而且他们过于昂贵，尤其是高分辨率的器件。制造高速转换器的一些工厂有：TRWLSIProducts, Datel-Intersil, puter Labs及Motorola。常用的并行转换器8位转换时间可到达30ns左右。要求