電子信息類專業(yè)英語Unit15TemperatureSensors課件

1、Unit 15 Temperature Sensors TextKey wordsTechnical termsExpressionsNotes to the textTextOne of the primary methods for electrical measurement of temperature involves changes in the electrical resistance of certain materials. In this, as well as other cases, the principle measurement technique is to

2、place the temperature-sensing device in contact with the environment whose temperature is to be measured. The sensing device then takes on the temperature of the environment. Thus a measure of its resistance indicates the temperature of the device and the environment must wait until the device comes

3、 into thermal equilibrium with the environment. The two basic devices used as the Resistance-Temperature Detector (RTD), based on the variation of metal resistance with temperature, and the thermistor , based on the variation of semiconductor resistance with temperature. There exists another depende

4、nce of electrical behavior of materials on temperature that forms the basis of a large percentage of all temperature measurement. This effect is characterized by a voltage-generating sensor in which an electromotive force (emf) is produced that is proportional to temperature. Such an emf is found to

5、 be almost linear with temperature and very repeatable for constant materials. Devices that measure temperature on the basis of this thermoelectric principle are called thermocouples (TCs). Here well briefly discuss the characteristics of Resistance-Temperature Detector (RTD).A Resistance-Temperatur

6、e Detector (RTD) is a temperature sensor that is based on the principles that metal resistance increasing with temperature. Metal used in these devices vary from platinum, which is very repeatable, quite sensitive, and very expensive, to nickel, which is not quits as repeatable, more sensitive, and

7、less expensive.Sensitivity An estimate of RTD sensitivity can be noted from typical values of a0, the linear fractional change in resistance with temperature. For platinum, this number is typically on the order of 0.004/, and for nickel a typical value is 0.005/. Thus, with platinum, for example, a

8、change of only 0.4 would be expected for a 100 RTD if the temperature is changed by 1. Usually, a specification will provide calibration information either as a graph of resistance versus temperature or as a table of values from which the sensitivity can be determined. For the same materials, howeve

9、r, this number is relatively constant because it is a function of resistivity.Response Time In general, RTD has a response time of 0.5 to 5 s or more. The slowness of response is due principally to the slowness of thermal conductivity in bringing the device into thermal equilibrium with its environm

10、ent.Construction A RTD, of course, is simply a length of wire whose resistance is to be monitored as a function of temperature. The construction is typically such that the wire is wound on a form (in a coil) to achieve small size and improve thermal conductivity to decrease response time. In many ca

11、ses, the coil is protective tube that inevitably increases response time but may be necessary in hostile environments. A loosely applied standard sets the resistance at multiples of 100 for a temperature of 0.Range The effective range of RTDs depends principally on the type of wire used as the activ

12、e element. Thus, a typical platinum RTD may have a range of 100 to 650, whereas a RTD constructed from nickel might typically have a specified range of 180 to 300.Key wordssensor n. 傳感器thermal adj. 熱的，熱量的equilibrium n. 平衡，平靜，均衡detector n. 探測器，檢波器，檢電器thermistor n. 熱敏電阻thermoelectric adj. 熱電的electromo

13、tive adj. 電動的thermocouple n. 物 熱電偶platinum n. 白金，鉑nickel n. 化鎳repeatable adj. 可重復(fù)的sensitivity n. 敏感，靈敏(度)，靈敏性fractional adj. 部分的calibration n. 標度，刻度，校準graph n. 圖表，曲線圖versus prep. 與相對resistivity n. 抵抗力，電阻系數(shù)conductivity n. 傳導(dǎo)性，傳導(dǎo)率inevitably adv. 不可避免hostile adj. 敵對的，敵方的Technical termstemperature-sensi

14、ng device 溫度敏感器件thermal equilibrium 熱量平衡Resistance-Temperature Detector (RTD) 電阻溫度計voltage-generating sensor 產(chǎn)生電壓的傳感器electromotive force (emf) 電動勢the active element 有源元件Expressionsin contact with 與相關(guān)，聯(lián)系come into 達到，得到based on 基于a large percentage of 很大的百分比be linear with與成線性on the basis of以為基礎(chǔ)Notes t

15、o the text1. In this, as well as other cases, the principle measurement technique is to place the temperature-sensing device in contact with the environment whose temperature is to be measured.無論何種測量，其測量技術(shù)的原理都是將溫度傳感裝置與被測溫的環(huán)境相接觸。句中，“to place the temperature-sensing device”至句末的不定式用作表語；“whose temperatu

16、re is to be measured”為定語從句，修飾“environment”；“to be measured”是從句中的不定式作表語成分。2. The two basic devices used as the Resistance-Temperature Detector (RTD), based on the variation of metal resistance with temperature, and the thermistor, based on the variation of semiconductor resistance with temperature.使用

17、的兩個測溫器件分別是電阻溫度計和熱敏電阻，其中前者是金屬電阻隨溫度變化而變化，后者是半導(dǎo)體電阻隨溫度變化而變化。句中的“based on the variation of metal resistance with temperature”修飾“ the Resistance-Temperature Detector (RTD)”；“based on the variation of semiconductor resistance with temperature”修飾“the thermistor”；“the Resistance- Temperature Detector”和“the thermistor”相并列。3. Metal used in these devices vary from platinum, which is very repeatable, quite sensitive, and very expensive, to nickel, which is no