测控技术与仪器专业英语课后阅读翻译

1、第五章课后A random erroris due to acontrolled，large number of independent small effects that cannothe identified orit is a statistical quantity. As such，iteach replication of the observations. If a large number of readings iswill vary for the same quantity.the scatter of the data about a mean value can b

2、e evaluated.The scatter generally follows a guassian distribution about a mean value.whichis assumed to be the true value.Accuracy is the deviation of the output from the calibration input or the truevalue. If the accuracy of a voltmeter is 2% full scale as described in the precedingsectionthe maxim

3、um deviation i、士2units for all readings.一个随机误差是由于控制,大量的独立影响小,不能他发现或这是一个统计量。因此,它每个复制的观察。如果大量的读数是同样数量的不同而不同。散射的数据值可以评估。散高斯分布通常遵循关于意味着value.which被认为是真正的价值。准确性是偏差的输出的输入或真正的校准价值。如果把电压表的准确性2%全面描述在前面的部分最大偏差我,士2units所有阅读资料。第五章.Noncontact Temperature Measurement Any object at any temperature above absolute z

4、ero radiates energy. This radiationvaries both in intensity and in spectral distribution with temperature. Hence.temperature may be deduced by measuring either the intensity or the spectrum of theradiation. The total energy density radiating from an idealblackbody(more on that later) isgiven by the

5、Stefan-boltzmann lawE=6Twhere E is energy density in W/cmz.6 Isthe Stefan-boltzmann constant(5. 6697 X 10 z W/cmz K)and T is the absolutetemperature(K).In other wordsthe total radiated energy is proportional to the fourthpower of the absolute temperature. A11 objects.particularly ideal blackbody obj

6、ects.also absorb incident radiation.(Uiven time to equilibrate.and presuming they are insulated from the heating or coolingeffects of surrounding air or other materials.they will eventually reach a point wherethey absorb and radiate energy at equal rates. ()ne consequence of this is that if an objec

7、t(a temperature sensor.for example) is an ideal blackbody.is perfectly insulated.and isflooded on its entire surface with radiation from a radiating source.it will eventuallyreach an equilibrium sources and blackbody calibration sources are available).thetemperature of the sensor is a measure of the

8、 temperature of the radiating object.任何物体在任何温度高于绝对零度的辐射能量。这种辐射无论是在不同强度和在光谱分布和温度。因此。通过测量温度可以推导出要么强度或频谱的辐射。总能量密度辐射从理想blackbody”(稍后详细介绍)鉴于法律的Stefan-boltzmannE = 6 T E在是能量密度在W / cmz。 6Stefan-boltzmann的常数(5。 6697 X 10 z W / cmz K”)和T是绝对的温度(K)。换句话说总辐射能量是成正比的第四绝对温度的力量。A11对象。特别是理想黑体对象。也会吸收入射辐射。(Uiven时间一致。和他

9、们隔绝放肆的加热或冷却周围空气的影响或其他材料。他们最终会达到一个临界点他们吸收和辐射能量在相同的利率。()东北的后果是,如果一个对象(一个温度传感器。例如)是一种理想的黑体。是完全绝缘。和是在整个表面淹没与辐射发射源。它最终将达到平衡来源和黑体校正源可用),温度传感器是一个测量辐射的温度对象。 An infrared radiation thermometer may be created in a manner similar to that inFigure 1 the radiated energy from the hot(or cold) object is focused on

10、a temperaturesensor.whose temperature then is indicative of the intensity of the radiation falling uponit. The sensor should be small and low mass for reasonable response time. Thermistorsoffer high sensitivity for low temperature measurements while thermocouples providethe operating range necessary

11、 for high levels of radiated energy. In some designs.thesensor is insulated from ambient conditions by placing it in a vacuum. The sensorsoutput is amplified.linearized.and fed to an output indicator or recorder. The optics are apt to be a bit different than shown in diagram. In mostapplications.par

12、ticularly at lower temperatures.much of the radiation will be farinfrared.which is not passed well by most glasses. It may be preferable to use areflective concave mirror to focus the incoming energy.rather than a lens. There mayalso be a red or infrared filter over the inlet to keep down interferen

13、ce due to strayambient light. For higher temperature use it may be necessary to reduce the totalincoming energy using a gray filter.shutter.or other obstruction. The Stefan-boltzmann law.and the proper operation of thesethermometers.presumes that theradiation is coming from a perfect blackbody radia

14、tor. to oversimplify(and it is not ourintention here to which does not reflect any radiation which may fall upon it. Allincident energy is absorbed. A non-blackbody object which reflects external radiationwill also reflect internally generated radiation.lowering the amount of energy radiated atany g

15、iven temperature.红外辐射温度计可以创建的方式类似,在图1的辐射能量从热(或冷)对象都聚焦在一个温度传感器。其温度然后表明辐射强度落它。应该是小的传感器和低质量为合理的响应时间。热敏电阻提供高灵敏度低温度的测量而热电偶提供必要的工作范围为高水平的辐射能量。在一些designs.the传感器是隔绝外界条件下通过将它放置在真空中。传感器的amplified.linearized输出。 和美联储到输出指标或录音机。光学往往稍有不同,图中所示。在大多数应用程序。特别是在较低的温度下。大部分的辐射将远红外线。这不是大多数眼镜了。这可能比使用凹面镜反射来聚焦入射能量。而不是一个镜头。也许也

16、是一个红色或红外过滤器在进口为了压制干扰由于流浪环境光。温度较高的使用可能需要减少总传入的能源使用灰色filter.shutter。 或其他阻塞Stefan-boltzmann的法律。 和适当的操作这些温度计。是假定辐射是来自一个完美的黑体的散热器。粗略的(和它不是我们的这里的意愿,没有反映出任何辐射可能落在它。所有入射能量被吸收。一个non-blackbody对象反映外部辐射也将反映出内部产生的辐射。降低辐射的能量在任何给定的温度。 Any surface has a reflectivity and an emissivity. Reflectivity，r，is simply the r

17、atioof reflected energy to incident energy:a perfect reflector has a reflectivity of one;ablackbody，zero. Emissivity，。，turns out to b simply。=1一re,fZecl:二:Cy reflectivity. Aperfect blackbody has emitted by an object at a given temperature is proportional to itsemissivity:a reflectivity object has em

18、issivity(we expect more heat from a rough，blackradiator than from a smooth，polished one). All this has a serious impact on radiation thermometry. An infrared radiationthermometer calibrated against a blackbody radiator will read seriously low when aimedat a reflective object .Most commercial radiati

19、on thermometers include a controlallowing the user to dial in the emissivity of the object being measured，plus a table oftypical emissivity values. Mist organic and nonmetallic materials have emissivity values.Most organic and nonmetallic materialshave emissivities between 0. 85 and 0. 95，whilemetal

20、s range roughly between 0. 1 and 0. 5(interestingly，both white and black paintshave similar emissivitie、一between 0. 9-at temperatures up to 1000C).任何表面具有反射率和发射率。反射率r,是简单的比率反射入射能量的能量:一个完美的反射器有一个反射率的;一个黑体,零。辐射率(。其实,b简单。= 1一re,fZecl:二:Cy反射率。一个完美的黑体物体所发出了在给定温度是成正比的辐射率:反射率对象有辐射率(我们希望更多的热量从粗糙的、黑色的散热器比从光滑、

21、磨光的一个)。所有这一切都有严重影响辐射测温。红外辐射对一个黑体温度计校准散热器将认真读书目的时低在反思对象。大多数商业辐射温度计包括控制允许用户来定下的热辐射特性被测对象,再加上一个表典型的辐射值。雾有机和非金属材料有辐射值。大多数有机和非金属材料有emissivities介于0。85年和年0。95年的时候,金属范围大致在0。1和0。5(有趣的是,两个白色和黑色颜料也有类似的emissivitie,一between 0。 9-at温度可达1000摄氏度)。 Variations in emissivitiy can cause serious errors，especially with m

22、etal surfaces.Highly polished surfaces have lower emissivity still farther. As an oxidation or coatingof the surfaces raises emissivity still farther. As an example，the emissivity of stainlesssteel at 8000C is when polished，0. 5 when rough machined，0. 7 when rough machinedand lightly oxidized and 0.

23、 8 to 0. 9 when heavily oxidized. If at all possible， the surfaceto be measured should be painted.oxidized.or otherwise made black and nonreflective.Liquid metals.a frequent application for infrared thermometry.are not as variable ittheir emissivity.but may be affected by layers of slag on their sur

24、face. It is a good ideato calibrated the infrared reading by making a contact temperature measurement or.itthe case of liquid metal.by plunging in a thermocouple as described in the previoussection. Also affecting the readings are atmospheric attenuation. Water vapor stronglyattenuates certain infra

25、red wavelengths while dust smoke.and particulate matter wilattenuate the radiation between the source and the sensor. Such problems are apt to bemost troublesome in industrial applications.emissivitiy变化可以导致严重的错误,尤其是在金属表面。高度抛光表面发射率低到更远。作为氧化或涂层表面发射率的提高到更远。作为一个例子,辐射率的不锈钢钢铁8000 C是当抛光,0。5当粗糙的加工,0。7当粗糙的加工

26、和轻氧化,0。8为0。9当严重氧化。如果可能的话,应该painted.oxidized surfaceto被测量。 或用其他的黑色和以及非反射。液态金属。一个频繁的应用程序为红外测温。不像变量他们的发射率。但可能会受层渣在其表面。这是一个好主意对校准红外阅读通过使接触or.it温度测量此案的液态金属。在一个热电偶大跌之前描述的那样部分。阅读资料也影响大气衰减。水蒸气强烈衰减某些波长红外线虽然灰尘烟。和颗粒物会衰减之间的辐射来源和传感器。这类问题是容易的摘要在工业应用中最麻烦的。 The dependence of the measurement upon emissivity can be r

27、educe by the use otwo-color pyrometry. As was mentioned at the start of this section.both the intensityand the spectral distribution of the radiation vary with temperature. The radianintensity at any wavelength.几.is given by:C 以J-一一一，二二一一二二干下尸一一一丁 expl l,/入1一1Where J is the radiant energy。is the emi

28、ssivity is the wavelengthand T is theabsolute temperature(K).On the assumption that emissivity is not a function owavelength(this assumption is not entirely true)the ratio of intensities at twcwavelengths becomes:测量的依赖性在辐射率可以减少使用o双色印铁测温。就像前面说过的在这一部分的开始。磁性的强度和光谱分布的辐射随温度。弧度在任何wavelength.几强度。 给出: C 以J-

29、一一一,二二一一二二干下尸一一一丁expl l, /入1一1这里J是辐射能.辐射率的是波长和T是吗绝对温度(K)。假设辐射率不是一个函数o波长(这种假设并不完全正确)的比例在twc公司的强度波长变得:测量的依赖性在辐射率可以减少使用o双色印铁测温。就像前面说过的在这一部分的开始。磁性的强度和光谱分布的辐射随温度。弧度在任何wavelength.几强度。 给出: C 以J-一一一,二二一一二二干下尸一一一丁expl l, /入1一1这里J是辐射能.辐射率的是波长和T是吗绝对温度(K)。假设辐射率不是一个函数o波长(这种假设并不完全正确)的比例在twc公司的强度波长变得:几.几/巨expCC=/J

30、，T一y/巨expCC=/J=T)一y 一一大一大Which may be simplified to=(consl)只exp大一大wherecn77s/丫)7了sC(几:/几)C(lid。一1/J,)第6章课后习题3.Uncertainty is generally stated as a numberindicating the tolerance from the true value of the measurand. T he tolerance is only estimated. It represents theconfidence level of the investiga

31、tor in the results.since the true value of themeasurement is unknown. he purpose of the sensor is to obtain dimensional information from theworkpiece. 。不确定性是一般表述数量表示宽容的过热蒸气的真实价值。他宽容只是估计T。它代表了信心水平的调查员在结果中。自从的真正价值测量是未知的。他的目的是获取维度信息的传感器从theworkpiece。 4. It is like a transducer in many instances because

32、 it converts oneenergy form to another. This other energy form is always an electrical signal.since we are considering sensors which provide an electrical signal to be used asfeedback to the process or machine control. 它就像一个传感器在许多情况下,因为它转换为一个能源形式到另一个。这其他能源形式总是一个电信号。因为我们正在考虑传感器提供一个电信号作为反馈过程或机器的控制。第六章

33、Eddy Current(Readihg Material) The eddy current sensor is similar in concept and performance to the capacitivesensor. It does have some differencesthoughthat may make it more suitable in someapplications. The major difference between the two sensors is the principle of operation. The eddy current se

34、nsor utilizes an electromagnetic field as opposed to thecapacitive electric field. It is the electromagnetic field that makes this noncontactingsensor much less sensitive to the effect of excited by a high-frequency alternating-currentsource. The resultant alternating magnetic field emanating from t

35、he coil generates eddycurrents in the near surface of the material being inspected. These currents.in turn.create their own magnetic field.which couples to the coil.superimposing a current onthe driving current. Demodulating circuitry detects this current signal.which can becalibrated to derive a di

36、stance is possible since the field strengths are a function of thedistance from the sensor to the target.电涡流传感器在概念上是类似和性能的电容传感器。它有一些差异但可能更适合在一些应用程序。这两者之间最大的不同在于传感器操作的原则。电涡流传感器利用电磁场的反对电容式电场。这是使这noncontacting电磁场传感器不太敏感的影响高频交流电兴奋不已源。由此产生的交变磁场散发的线圈生成艾迪电流的近表面的材料被检查。这些电流。反过来。创建他们自己的磁场。这夫妇线圈。叠加一个电流驱动电流。检测电

37、流信号的解调电路。可以校准中派生出的距离是可能的因为这个领域的优势是一个函数距离从传感器到目标。 Progressing required for the analog output of this type of sensor is identical to thatfor the capacitive sensor. Resolution is limited by the A/D converter. Spot size.range.and standoff distance are comparable to those available in a capacitive device

38、. Aconductive work piece is required to support the induced currents. Concerning spot size.the eddy current probe has limitations in terms of how small acoil.with enough turns to generate a sufficient magnetic field.can be wound. Sincefringe fields have an effect on the output.the eddy current probe

39、 is also limited toconstant-geometry situations where these errors can be determined and calibrated out.Since this device depends on eddy currents.which are a near-surface phenomenonthereare other variables peculiar to this sensor that must understood. The strength of the induced magnetic field is a

40、 function of the condition of thematerial. Because different materials have different resistivities.the sensor must becalibrated for a specific material. In addition.other material characteristics such asporosity and density affect the output. Near-surface conditions including defects such ascracks

41、or inclusions alter the output and may be indistinguishable from changes in thedistance being measured. Indeed.the primary use of this type of sensor is for surfaceand near-surface material defects.to which it is very sensitive. iJltrasoundSound waves can be utilize by ranging to obtain dimensional

42、information. The configuration of the sensor involves a transmitter of sound energy and receiver. In manycases the transmitter and receiver are in the same unit. Distance information is obtainedby measuring the transit time required for the echo the return. Since the speed of soundin the medium is k

43、nown, distance can be determined directly from time-of-flightinformation.进步的模拟输出所需的这种类型的传感器是一致的电容式传感器的。决议是有限的,由A / D转换器。size.range现货。和靶距同电容装置中可用。一个导电工件必须支持诱发的电流。关于现货大小。电涡流探测器方面的限制如此小的一段线圈。有足够的转向生成足够的磁场。可以伤口。自从边缘领域影响输出。电涡流探头也仅限于constant-geometry这些错误的情况下可以确定和校准出来。因为这个设备取决于涡流。这是一个近地表现象?其他变量所特有的,这种传感器,必

44、须理解。强度的感应磁场是一个函数的状况材料。因为不同的材料有不同的电阻率。传感器必须校准,为特定的材料。此外。其他材料等特点孔隙率和密度影响输出结果。近地表条件包括等缺陷裂缝或包裹体改变输出和可能与改变距离被测量。事实上。主要使用这种类型的传感器是表面的和近地表材料缺陷。它是非常敏感的。iJltrasound声波可以利用测距获取维度信息。传感器的配置包括发射机和接收机的声音的能量。在许多情况下,发送器和接收器在同一个单元。距离信息被获取通过测量交通所需时间回声返回。因为声音的速度在中是已知的,距离可以直接从tofms决定信息。 Ultrasonic energy.which is beyond

45、 the audible frequency range.is normallyutilized since the wavelength of audible sound energy is relatively long compared withthe resolution required for most dimensional measurements. For higl:一resolutionapplications.with measurement resolutions finer than 0. 1 in. , a liquid couplant(typically wat

46、er) is required because the sound energy at the higher frequencies is highlyattenuated in air. In an inprocess measurement application.water-or oil-based cuttingfluids can serve as a coupling medium. The workpiece under measurement need not beimmersed as a continuous stream of liquid can adequately

47、convey the sound. The transmitter/receiver for an ultrasonic sensor is typicallyThe crystal itself is mechanically damped in order to attenuatea piezoelectric crystal. oscillation and avoidmasking the weak incoming echoes. The pulser is a fast.higl:一voltage switch that drivesthe transducer with a sh

48、ort rise time pulse that is converted into a mechanical pressurewave. The longitudinal sound wave is conveyed by the medium to the target.where it isreflected back to the transducer. The same crystal or an identical one converts the echoto an electrical impulse.which is amplified by a tunedA timer i

49、s generally triggered by the pulse unitamplifier.and disabled by receipt of theincoming echo. The value held by the timer is the time of flight of the sound wave.thatis.the time it takes the sound is constant for homogenous materials at a fixedtemperature.the distance to the target can be determined

50、 by multiplying the speed bythe time and dividing the result by two to get a single path length. Digital counter/timers are presently utilized with ultrasonic sensors and provide direct digitalinformation for transmission over serial or parallel data links.超声能量。那是超越声的频率范围内。通常是利用自波长的声波能源相对比较长相比该决议要求对

51、大多数尺寸测量。对于higl:一resolution应用程序。测量分辨率这些比0。1。,液体耦合剂(通常是水)是有必要的,因为在高频率的声音的能量是高度在空气中减毒活疫苗。在一个inprocess测量应用程序。水油性切削液体可以作为一个耦合介质。在测量工件不需要作为一个连续的流浸入液体可以充分表达的声音。这个发射器/接收器进行超声波传感器通常是水晶本身是机械阻尼为了减弱压电晶体。振荡和避免屏蔽弱传入的回声。是一个快速的脉冲源。higl:一voltage开关,驱动器该传感器与短脉冲上升时间将被转换成一个机械压力波。纵向声波是靠中长期目标。它在哪里反射回换能器。同样的水晶或等同将呼应电冲动。这是一

52、个调谐放大了吗通常一个计时器触发脉冲单元放大器。和残疾的收据传入的回声。持有价值定时器的飞行时间wave.that的声音是。花费的时间听起来是常数同质材料在一个固定的温度。距离目标可以确定乘以速度时间和划分结果由两位得一个路径长度。数字计数器/计时器是目前利用超声波传感器,提供直接的数字信息传输串行或并行数据链接。 The spot size of the noncontact ultrasonic sensor is determined by the size of thewave front of the sound energy. This size id in turn govern

53、ed by the configuration of thetransducer.which may have a lens incorporated to it to permit a focused spot. This spotsize may range from approximately 0. 05 to 1.0 contacting transducers discussed here.tends to average the information received from the target. Different form other sensors.however.th

54、e returning sound waves reflected fromvarying distances to the target integrated over the spot size cause a dispersion of the itemsignal which may result in trouble establishing an exact time reading.especially in cases where a constant thresholding circuit encounters varying amplitude signals. This

55、problem can be overcome .however.when the geometry of the workpiece is known orwhen the sensor is kept normal to the workpiece. Under these circumstances.accuraciesfor this type of sensor of 0. 0001 to 0. 001 in. can be achieved.现场的非接触式的大小决定了超声波传感器的尺寸波前的声音的能量。这个尺寸id反过来由配置的传感器。这可能有一个镜头融入到其中,它允许一个集中位置

56、。这地方大小可以从大约0。05到1.0联系这里讨论换能器。倾向于平均收到的信息从目标。其他sensors.however形式不同。 返回的声波反射不同距离的目标集成在现货大小造成的分散项目信号,它可能导致麻烦建立具体时间阅读。特别的情况下,有一个常数电路遇到不同幅度信号的阈值。这此问题是可以克服的。当几何形状的工件是已知或当传感器保持正常的工件。在这些circumstances.accuracies对于这种类型的传感器为0。0001年到0。 可以达到001英寸。现场的非接触式的大小决定了超声波传感器的尺寸波前的声音的能量。这个尺寸id反过来由配置的传感器。这可能有一个镜头融入到其中,它允许一个

57、集中位置。这地方大小可以从大约0。05到1.0联系这里讨论换能器。倾向于平均收到的信息从目标。其他sensors.however形式不同。 返回的声波反射不同距离的目标集成在现货大小造成的分散项目信号,它可能导致麻烦建立具体时间阅读。特别的情况下,有一个常数电路遇到不同幅度信号的阈值。这此问题是可以克服的。当几何形状的工件是已知或当传感器保持正常的工件。在这些circumstances.accuracies对于这种类型的传感器为0。0001年到0。 可以达到001英寸。 Standoff distances in the range of a fraction of an inch to tens of feet are possiblewith ultra