热电偶温度传感器中英文对照外文翻译文献
热电偶英文标记
热电偶英文标记A thermocouple, also known as a hot junction pair, is a type of sensor used to measure temperature in various industries. The English label for a thermocouple is typically "TC." Thermocouples work on the principle of Seebeck effect, where a voltage is generated when there is a temperature difference between the two junctions of the sensor.热电偶，也称为热接点对，是一种用于各种工业中测量温度的传感器。
热电偶的英文标记通常是"TC"。
热电偶的工作原理是基于塞贝克效应，即在传感器的两个接头之间存在温度差时会产生电压。
One of the key advantages of thermocouples is their ability to measure a wide range of temperatures, from cryogenic levels to extremely high temperatures. This versatility makes them suitable for a variety of industrial applications where temperature monitoring is critical for operational efficiency and safety.热电偶的一个主要优势是其能够测量从低温到极高温范围内的温度。
这种多功能性使它们适用于各种工业应用，其中温度监测对于操作效率和安全至关重要。
热释电红外传感器中英文对照外文翻译文献
热释电红外传感器中英文对照外文翻译文献中英文对照翻译热释电红外传感器前言热释电红外传感器是一种非常有应用潜力的传感器。
它能检测人或某些动物发射的红外线并转换成电信号输出。
早在1938年，有人就提出利用热释电效应探测红外辐射，但并未受到重视。
直到六十年代，随着激光、红外技术的迅速发展，才又推动了对热释电效应的研究和对热释电晶体的应用开发。
近年来，伴随着集成电路技术的飞速发展，以及对该传感器的特性的深入研究，相关的专用集成电路处理技术也迅速增长。
本文先介绍热释电传感器的原理，然后再描述相关的专用集成电路处理技术。
热释电效应在自然界，任何高于绝对温度（-273K）的物体都将产生红外光谱，不同温度的物体释放的红外能量的波长是不一样的，因此红外波长与温度的高低是相关的，而且辐射能量的大小与物体表面温度有关。
可见光的波长通常在1μm以下，而1μm以上的光人眼是看不到的，但是可以通过适当的仪器对辐射的能量进行检测。
当一些晶体受热时，在晶体两端将会产生数量相等而符号相反的电荷，这种由于热变化产生的电极化现象，被称为热释电效应。
通常，晶体自发极化所产生的束缚电荷被来自空气中附着在晶体表面的自由电子所中和，其自发极化电矩不能表现出来。
当温度变化时，晶体结构中的正负电荷重心相对移位，自发极化发生变化，晶体表面就会产生电荷耗尽，电荷耗尽的状况正比于极化程度，图1表示了热释电效应形成的原理。
能产生热释电效应的晶体称之为热释电体或热释电组件，其常用的材料有单晶(LiTaO3 等)、压电陶瓷（PZT等）及高分子薄膜（PVFZ等）[2]当以LiTaO3为代表的热释电材料处于自极化状态时，吸收红外线入射波后，结晶的表面温度改变，自极化也发生改变，结晶表面的电荷变得不平衡，把这种不平衡电荷的电压变化取出来，便可测出红外线。
热释电材料只有在温度变化时才产生电压，如果红外线一直照射，则没有不平衡电压，一旦无红外线照射时，结晶表面电荷就处于不平衡状态，从而输出电压。
温度传感器外文翻译
英文翻译Temperature humidity sensorThe sensor in type many sensors, the temperature sensor and applies two aspects in its output both is second to and with it correlation temperature is an important physical parameter, he affects all physical, chemistry and biomedicine process march, regardless of in the industry, the agriculture, the scientific research, the national defense and people's daily life each aspect, the temperature survey and the control all is the extremely important with the electronic technology and the materials science development, to each kind of new thermal element and the temperature sensor request structure advanced, the performance is stable, satisfies the more and more high request which proposed to the temperature survey and the control.Sensor classification carries on classified resistance type PN according to the manufacture temperature sensor material and the principle of work to tie the type thermoelectricity type radiation formular operating region is refers to the resistance value to have the remarkable change temperature sensor along with the temperature change, it may transform directly the temperature as the electrical the operating temperature scope, its resistance the which increases along with the temperature ascension is called positive temperature coefficient (PTC); Its resistance number the which reduces along with the temperature t ascension is called negative temperature (NTC); The negative temperature which reduces suddenly along with the temperature rise is called critical (CTR) in a warm area internal resistance.1. PTC principle of the PTC r usually to use the (BaTio3) ceramic material, the pure BaTio3 ceramics have the extremely high electronic resistivity under often the temperature, above 108Ω · m, therefore is the insulator.If carries on the doping in BaTio3, may cause the BaTio3 semiconductor, for example: Mixes by %% rare-earth element, but causes it to become has under the normal temperature----10Ω · m N line of semiconductors .Has electricity semiconductor BaTio3, when the temperature achieved when Curie temperature T, it transforms by the tetragonal system into the cubic system, this time its electronic resistivity leap increases several magnitudes ( times).Positive temperature coefficient the (PTC) acts according to this nature manufacture.After in semiconductor multi-crystal grain structure BaTio3, its crystal grain (general size small is approximately 3-10 µ m) the interior is the semiconductor nature; But the crystal boundary (has f e r r o electricity) for the high-resistance area. When type crystal external voltage, voltage majority of landings on high-resistance crystal boundary level, thus the crystal boundary has an effect to the material electric conductivity .The electron must pass through the crystal boundary barrier potential barrier from a crystal grain to be able to arrive another crystal grain .Below Curie temperature T c, BaTio3 is tetragonal system dielectric, the existence has the spontaneous polarized very strong internal electric field, enable the electron to have the high energy, thus the traversing crystal boundarypotential barrier is easy. But above Curie temperature T c, BaTio3 becomes the cubic system by the tetragonal system, polarizes vanishing spontaneously, internal electric field vanishing, the electricity is difficult in the traversing potential barrier, therefore above curie warm waste T c, electronic resistivity sharp increase. When two crystal grains contact mutually, crystal grain barrier potential barrier as shown in Figure is potential barrier le vel thickness, ø0 is the barrier height .According to the equation, the barrier height ø0 sticks the effective dielectric constant εe ff between with the crystal the relations is: In the formula, n0 is the density of donors; e is t he electronic electric quantity .ε0 is the vacuum coefficient of d i electrical loss. When the electronic overstepping potential barrier enters ø0, the electronic resistivity may write isWhen the temperature is l ower than Curie temperature TC, εe ff the value is approximately about 104, therefore ø0 very small, the ceramic electronic resistivity rho approaches in the volume resistivity ρv, after the temperature surpasses Curie temperature TC, the value drops suddenly, the A value increases, causes rho the value sharp increase, dopes BaTio3 and rho and between the temperature relational like chart .NTC t h r principle of work NTC the r s tor majority is by the transition family metal oxide compound (mainly is with M n, co, Ni, Fe and so on), the agglutination forms the semiconductor metal oxide compound under the controlled condition, they only have the P semiconductor characteristic .Regarding the common semiconducting material, the electronic resistivity mainly is relies on along with the warm waste change the current carrier number along with the temperature change, the temperature increment, the current carrier number increases, electric conduction ability enhancement. Thus electronic resistivity F falls. Regarding transition metal oxide compound semiconductor, for example Ni O, because its acceptor ionizing energy is very small, broad basic ionized completely in the room temperature, namely the current carrier density basically has nothing to do with the temperature, this time, should mainly consider the transport ratio and the temperature relations .By the semiconductor physics knowledge, the transport ratio expresses by the equation below:In the formula: The d-- oxygen octahedron gap is away from (Ni O is the Na Cl structure); V0-- lattice vibration frequency; The Ei-- activation energy, indicated the electron jumps originally from one in the position the energy which needs to the neighboring atom site. Or rewriting Then the electronic resistivity is: 0Ne-Ei/kT If command, then type changes: rho =ρ0eEi/KT Obviously the metal oxide compound semiconductor electronic resistivity mainly has the transport ratio along with the temperature change to cause along with the temperature change .When temperature increment, the electronic resistivity drops, assumes the negative temperature coefficient characteristic. Critical temperature also belongs to the negative temperature coefficient. But in some critical temperature scope, its resistance number drops suddenly along with the temperature rise .Anti- as shown in Figure 4-4. In the chart the anti- r curve has aresistance number point of discontinuity, approximately for 68℃, resistance number point of discontinuity magnitude generally in 3~ carry on the adjustment based on the material ingredient, it is suitable specially in 65℃~75℃ between uses, this kind of resistor may make the constant temperature control and on-off element.The CTR r usually uses the glass semiconductor processing, take the vanadium as the main material. Mixes in certain materials and so on oxide compound like C a O, B a O, S O or P2O5, TiO2 becomes after the hot dissolve. temperature sensor basic characteristic in view of the fact that the temperature sensor type is many, moreover its work mechanism is also different. This mainly introduces t the hot sensitive diode and the hot sensitive transistor characteristic and the parameter. from the s the material and anti- and so on carry on the classification variously. According to structure shape classification: Laminated shape, gasket shape, rod-shaped, tubular, thin membrane, thick membranous and other shapes. Includes according to the anti- temperature ra classification: Normal temperature, high temperature and ultralow temperature hot sensitive resistor. Includes according to the anti- classification: Negative temperature coefficient r (NTC), switch temperature r (PTC); Slow aberration positive temperature coefficient r (PTC), the critical negative temperature coefficient, the platinum resistor limits the temperature curve like chart 4-4 curvature 1. 1st, resistance - temperature characteristic anti- is refers to between the actual resistance value and the resistance body temperature dependent relations, this is one of basic characteristics.PTC switch positive temperature coefficient anti- curve. value rises suddenly to some temperature nearby the maximizing.Through the doping .If dopes P b in BaTio3, may cause Tc to the high temperature traverse, mixes in elements and so on S r or S n after BaTio3, may cause TC to the low temperature traverse. May according to need to adjust t Curie temperature TC. The actual resistance number expressed with RT. Is under certain ambient temperature, uses causes the resistance number change not to surpass the resistance value which % survey power actual resistance value is called the zero energy resistance value, or is called does not give off heat the power resistance value (cold resistance value).The actual resistance value size is decided by the resistor material and the geometry shape. If the actual resistance number own temperature has the following relations: NTC In the formula: RT time 11 temperature T actual resistance value; R 1 and resistance geometry shape with material related constant B, A 11 material constants. For the easy to operate, usually takes the ambient temperature for 25℃ to take the reference temperature, then has: NTC puts the resistor hotly: RT/R25=exp[B(1/T-1/298)] PTC g change along with the temperatureT change, and is proportional with material constant B. Therefore, usually while gives the resistance temperature coefficient, must point out when the survey temperature, positive temperature coefficient t a T in value superior constant A. Slow aberration positive temperature coefficient value in %/℃ 110%/℃ between. But the switch(mutant) positive temperature co efficient T may achieve 60%/℃ or higher. Material constant B is uses for to describe the t material physical property - parameter. Also is called the thermal sensitivity target. In the operating region, the B value is not a strict constant, has slightly along with the temperature ascension increases .In general, the B value great electronic resistivity is also high. The different B value material has the different use, like ordinary negative temperature coefficient material constant B value between 2000yi5000 K. The negative temperature coefficient B value may according to the equation below computation: Positive temperature coefficient resistor, its A value according to equation below computation: In the formula, R1 R2 respectively is time thermodynamic temperature T1 and the T2 resistance value. 2. thermal properties (1) dissipation constant H dissipation constant H defined as the temperature each increase once diffusion power .It uses for when describes work, the resistance element and the external environment carry on the hot conversation a physical quantity. Dissipation constant H and dissipated power P .The temperature increment AT relations are The H size and the t structure, locates the environment medium type, the velocity of movement, the pressure and the heat conduction performance and so on related, when ambient temperature change, H has the change. (2) capacity and the time-constant r appliance has certain calorific capacity C, therefore it has certain warm. Also is the temperature change needs certain time. When the is heated up the T2 temperature, puts to the temperature is in the T0 environment, does not add the electric power, the starts to decrease temperature, its temperature T is the time t function, in △t time. The may indicate to the environment diffusion quantity of heat is: H(T-T0)△t, this part of quantity of heat is provides by the temperature decrease. Its value for - C△T, therefore has:Expressed in the environment atmosphere the steam content physical quantity is a y. The humidity expression method has two kinds, namely absolute humidity and relative h um (RH).The absolute humidity is refers to in the atmosphere the water content absolute value, the relative humidity is refers to in the atmosphere the steam to press with the identical temperature under ratio of the saturated steam tension, expressed with the percentage. The humidity sensor or the dew cell are refer to the paraphrase to the humidity sensitive part, it may be the wet sensitive resistor, also may be the wet sensitive capacitor or other dew cells. The humidity sensor classification classifies according to the feeling wet physical quantity, the humidity sensor may divide into three big kinds, namely wet sensitive resistor, wet sensitive capacitor and wet sensitive transistor. The humidity resistor makes which according to the use different material may divide into: Metal oxide compound semiconductor ceramics wet sensitive resistor, for example: MgCr2O4 series, ZnO-Cr2O3 series; Element material wet sensitive resistor, for example: Semiconductor G e, Si, Se and C element; Compound wet sensitive resistor, for example: Li Cl, CaSO4, and fluoride and iodide and so on; High polymer wet sensitive resistor and so on. The wet sensitive capacitor mainly is the porous Al2O3material makes as the medium. The wet sensitive transistor divides into the wet sensitive diode and the wet sensitive three levels of tubes. The wet sensitive resistor principle of work and the characteristic 1, the metal oxide compound semiconductor ceramics wet sensitive resistor (1) principle of work porous metal oxide compound semiconductor ceramics, in the crystal plane and the crystal boundary place, very easy to adsorb t drone. Because the water is one strong polar dielectric medium, nearby the h y drone hydrogen atom has the very strong electric field, has the very big electron affinity. When h y drone adheres to stick cohere when the semiconductor ceramics surface, will form the energy level very deep attachment surface acceptor condition, but from semiconductor ceramics surface capture electron, but will form the bound state in the ceramic surface the negative space charge, correspondingly will appear the hole in the near surface layer to accumulate, thus will cause the semiconductor ceramics electronic resistivity depression.Moreover, according to the ion electric conductance principle, the structure not compact semiconductor ceramics crystal grain has certain crevice, reveals the porous capillarity tubular .The drone may adsorbs through this kind of pore between various crystal grains surface and the crystal grain, because adsorbs the e separable relieves the massive electric conduction ion, these ions are playing the electric charge transportation role in the water adsorbed layer. along with humidity increase, material electronic resistivity drop. oxide compound semiconductor ceramics wet sensitive resistor principal variety and structure The metal oxide compound semiconductor ceramics wet sensitive resistor typical product includes: MgCr2O4 - TiO2 wet sensitive resistor, ZnO-Cr2O3 wet sensitive resistor, ZnO-Li2O3-V2O5 wet sensitive resistor and so on. For example: The ZnO-Li2O3-V2O5 wet sensitive resistance, is take Zn O as the main material, is joining a price, two prices, three prices and so on other metal oxide compound burns the ceramics semiconducting material, the survey humidity scope is 5%~100%RH, the measuring accuracy is 2%, is one kind of more ideal dew cell, and may make the miniaturization, the structure is simple. 2nd, element material wet sensitive resistor kind of wet sensitive resistor is a part which the element semiconducting material or the element material make.The carbon wet sensitive resistor is one resistance - humidity characteristic is the dew cell. With the organic matter polypropylene plastic piece or the stick are substrates, spreads cloth one to include the conductive carbon granule organic textile fiber constitution. This kind of wet sensitive resistor craft is simple, is advantageous for the uses the organic material absorption of moisture, the volume expansion, between the carbon granule distance increases, thus the resistance value increases principle. The element semiconductor, have on the honeycomb electrode ceramic substrate, is composed [granule diameter by the characteristic in the Fe3O4 colloid by the particle approximately for (100~250)×10-8m], each pellet only then a magnetic domain, therefore, the co current pellet attracts the union mutually, thus does not need the highpolymer material to make the colloid bond, but can obtain the good performance and the long service life. Figure 4-1 is the Fe3O4 colloid wet sensitive resistor structure drawing. Figure 4-2 is the Fe3O4 wet sensitive resistor resistance humidity characteristic curve, displays for the negative feeling wet characteristic. 4th, the wet sensitive resistor characteristic (1) resistance - humidity characteristic wet sensitive resistor resistance number along with the humidity change is generally the index relations change.温度传感器在种类繁多的传感器中，温度传感器在其产量和应用两方面都是数一数二的。
温度变送器中英文对照外文翻译文献
中英文对照外文翻译中英文资料对照外文翻译TT302 温度变送器概述TT302温度变送器接收毫伏(mV)输出的信号，这类传感器包括热电偶或阻性传感器，例如：热电阻（RTD）。
它所接受的信号必须在允许的输入范围之内。
允许输入电压范围为-50到500，电阻范围为0到2000欧姆。
功能描述-硬件每个板的功能介绍如下：图2.1 TT302-硬件构成方框图多路转换器多路转换器将变送器端子接到相应信号调理板上，以保证在正确的端子上测量电压。
信号调理板他的作用给输入信号提供一个正确的值以满足A/D转换。
A/D转换器A/D转换器将输入信号转换成数字形式传给CPU。
信号隔离他的作用在输入和CPU之间隔离控制信号和数字信号。
中央处理单元（CPU）RAM PROM和EEPROMCPU是变送器的智能部分，主要完成测量，板的执行，自诊断和通信的管理和运行。
系统程序存储在PROM中。
RAM用于暂时存放运算数据。
在RAM中存放的数据一旦断电立即消失，所以数据必须保存在不易丢失的EEPROM中。
例如：标定，块的标识和组态等数据。
通信控制器监视在线动态，调整通信信号，插入，删除预处理，滤波。
电源变送器电路通过现场总线电源供电。
电源隔离像信号隔离一样，供给输入部分的信号必须要隔离，电源隔离采用变压器将直流供电电源转换成高频交流供电。
显示控制器从CPU接收数据送给LCD显示器的显示部分，此时显示器必须处于打开状态。
本机调整它有两个磁性驱动开关，它们必须由磁性工具来驱动而不是机械或电的接触。
图2.2-LCD指示器温度传感器TT302像前面所描述的那样，可以兼容多种类型的传感器。
TT302为使用热电偶或热电阻RTD 测量温度进行了特殊设计。
此类传感器的基本内容如下所述：热电偶热电偶由两种不同的金属或合金在一端连接在一起所组成的，被称为测量端或热端。
测量端必须放在测量点上，热电偶的另一端是打开的连接在温度变送器上，这一端称做参考端或冷端。
在大多数应用中，塞贝克效应可以充分解释热电偶的工作原理。
传感器的基础知识中英文对照外文翻译文献
中英文对照外翻译Basic knowledge of transducersA transducer is a device which converts the quantity being measured into an optical, mechanical, or-more commonly-electrical signal. The energy-conversion process that takes place is referred to as transduction.Transducers are classified according to the transduction principle involved and the form of the measured. Thus a resistance transducer for measuring displacement is classified as a resistance displacement transducer. Other classification examples are pressure bellows, force diaphragm, pressure flapper-nozzle, and so on.1、Transducer ElementsAlthough there are exception ,most transducers consist of a sensing element and a conversion or control element. For example, diaphragms,bellows,strain tubes and rings, bourdon tubes, and cantilevers are sensing elements which respond to changes in pressure or force and convert these physical quantities into a displacement. This displacement may then be used to change an electrical parameter such as voltage, resistance, capacitance, or inductance. Such combination of mechanical and electrical elements form electromechanical transducing devices or transducers. Similar combination can be made for other energy input such as thermal. Photo, magnetic and chemical,giving thermoelectric, photoelectric,electromaanetic, and electrochemical transducers respectively.2、Transducer SensitivityThe relationship between the measured and the transducer output signal is usually obtained by calibration tests and is referred to as the transducer sensitivity K1= output-signal increment / measured increment . In practice, the transducer sensitivity is usually known, and, by measuring the output signal, the input quantity is determined from input= output-signal increment / K1.3、Characteristics of an Ideal TransducerThe high transducer should exhibit the following characteristicsa) high fidelity-the transducer output waveform shape be a faithful reproduction of the measured; there should be minimum distortion.b) There should be minimum interference with the quantity being measured; the presence of the transducer should not alter the measured in any way.c) Size. The transducer must be capable of being placed exactly where it is needed.d) There should be a linear relationship between the measured and the transducer signal.e) The transducer should have minimum sensitivity to external effects, pressure transducers,for example,are often subjected to external effects such vibration and temperature.f) The natural frequency of the transducer should be well separated from the frequency and harmonics of the measurand.4、Electrical TransducersElectrical transducers exhibit many of the ideal characteristics. In addition they offer high sensitivity as well as promoting the possible of remote indication or mesdurement. Electrical transducers can be divided into two distinct groups:a) variable-control-parameter types,which include:i)resistanceii) capacitanceiii) inductanceiv) mutual-inductance typesThese transducers all rely on external excitation voltage for their operation.b) self-generating types,which includei) electromagneticii)thermoelectriciii)photoemissiveiv)piezo-electric typesThese all themselves produce an output voltage in response to the measurand input and their effects are reversible. For example, a piezo-electric transducer normally produces an output voltage in response to the deformation of a crystalline material; however, if an alternating voltage is applied across the material, the transducer exhibits the reversible effect by deforming or vibrating at the frequency of the alternating voltage.5、Resistance TransducersResistance transducers may be divided into two groups, as follows:i) Those which experience a large resistance change, measured by using potential-divider methods. Potentiometers are in this group.ii)Those which experience a small resistance change, measured by bridge-circuit methods. Examples of this group include strain gauges and resistance thermometers.5.1 PotentiometersA linear wire-wound potentiometer consists of a number of turns resistance wire wound around a non-conducting former, together with a wiping contact which travels over the barwires. The construction principles are shown in figure which indicate that the wiperdisplacement can be rotary, translational, or a combination of both to give a helical-type motion. The excitation voltage may be either a.c. or d.c. and the output voltage is proportional to the input motion, provided the measuring device has a resistance which is much greater than the potentiometer resistance.Such potentiometers suffer from the linked problem of resolution and electrical noise. Resolution is defined as the smallest detectable change in input and is dependent on thecross-sectional area of the windings and the area of the sliding contact. The output voltage is thus a serials of steps as the contact moves from one wire to next.Electrical noise may be generated by variation in contact resistance, by mechanical wear due to contact friction, and by contact vibration transmitted from the sensing element. In addition, the motion being measured may experience significant mechanical loading by the inertia and friction of the moving parts of the potentiometer. The wear on the contacting surface limits the life of a potentiometer to a finite number of full strokes or rotations usually referred to in the manufacture’s specification as the ‘number of cycles of life expectancy’, a typical value being 20*1000000 cycles.The output voltage V0 of the unload potentiometer circuit is determined as follows. Let resistance R1= xi/xt *Rt where xi = input displacement, xt= maximum possible displacement, Rt total resistance of the potentiometer. Then output voltage V0= V*R1/(R1+( Rt-R1))=V*R1/Rt=V*xi/xt*Rt/Rt=V*xi/xt. This shows that there is a straight-line relationship between output voltage and input displacement for the unloaded potentiometer.It would seen that high sensitivity could be achieved simply by increasing the excitation voltage V. however, the maximum value of V is determined by the maximum power dissipation P of the fine wires of the potentiometer winding and is given by V=(PRt)1/2 .5.2 Resistance Strain GaugesResistance strain gauges are transducers which exhibit a change in electrical resistance in response to mechanical strain. They may be of the bonded or unbonded variety .a) bonded strain gaugesUsing an adhesive, these gauges are bonded, or cemented, directly on to the surface of the body or structure which is being examined.Examples of bonded gauges arei) fine wire gauges cemented to paper backingii) photo-etched grids of conducting foil on an epoxy-resin backingiii)a single semiconductor filament mounted on an epoxy-resin backing with copper or nickel leads.Resistance gauges can be made up as single elements to measuring strain in one direction only,or a combination of elements such as rosettes will permit simultaneous measurements in more than one direction.b) unbonded strain gaugesA typical unbonded-strain-gauge arrangement shows fine resistance wires stretched around supports in such a way that the deflection of the cantilever spring system changes the tension in the wires and thus alters the resistance of wire. Such an arrangement may be found in commercially available force, load, or pressure transducers.5.3 Resistance Temperature TransducersThe materials for these can be divided into two main groups:a) metals such as platinum, copper, tungsten, and nickel which exhibit and increase in resistance as the temperature rises; they have a positive temperature coefficient of resistance.b) semiconductors, such as thermistors which use oxides of manganese, cobalt, chromium, or nickel. These exhibit large non-linear resistance changes with temperature variation and normally have a negative temperature coefficient of resistance.a) metal resistance temperature transducersThese depend, for many practical purpose and within a narrow temperature range, upon the relationship R1=R0*[1+a*(b1-b2)] where a coefficient of resistance in ℃-1,and R0 resistance in ohms at the reference temperature b0=0℃ at the reference temperature range ℃.The international practical temperature scale is based on the platinum resistance thermometer, which covers the temperature range -259.35℃ to 630.5℃.b) thermistor resistance temperature transducersThermistors are temperature-sensitive resistors which exhibit large non-liner resistance changes with temperature variation. In general, they have a negative temperature coefficient. For small temperature increments the variation in resistance is reasonably linear; but, if large temperature changes are experienced, special linearizing techniques are used in the measuring circuits to produce a linear relationship of resistance against temperature.Thermistors are normally made in the form of semiconductor discs enclosed in glass vitreous enamel. Since they can be made as small as 1mm,quite rapid response times are possible.5.4 Photoconductive CellsThe photoconductive cell , uses a light-sensitive semiconductor material. The resistance between the metal electrodes decrease as the intensity of the light striking the semiconductor increases. Common semiconductor materials used for photo-conductive cells are cadmium sulphide, lead sulphide, and copper-doped germanium.The useful range of frequencies is determined by material used. Cadmium sulphide is mainly suitable for visible light, whereas lead sulphide has its peak response in the infra-red regionand is, therefore , most suitable for flame-failure detection and temperature measurement. 5.5 Photoemissive CellsWhen light strikes the cathode of the photoemissive cell are given sufficient energy to arrive the cathode. The positive anode attracts these electrons, producing a current which flows through resistor R and resulting in an output voltage V.Photoelectrically generated voltage V=Ip.RlWhere Ip=photoelectric current(A),and photoelectric current Ip=Kt.BWhere Kt=sensitivity (A/im),and B=illumination input (lumen)Although the output voltage does give a good indication of the magnitude of illumination, the cells are more often used for counting or control purpose, where the light striking the cathode can be interrupted.6、Capacitive TransducersThe capacitance can thus made to vary by changing either the relative permittivity, the effective area, or the distance separating the plates. The characteristic curves indicate that variations of area and relative permittivity give a linear relationship only over a small range of spacings. Thus the sensitivity is high for small values of d. Unlike the potentionmeter, the variable-distance capacitive transducer has an infinite resolution making it most suitable for measuring small increments of displacement or quantities which may be changed to produce a displacement.7、Inductive TransducersThe inductance can thus be made to vary by changing the reluctance of the inductive circuit. Measuring techniques used with capacitive and inductive transducers:a)A.C. excited bridges using differential capacitors inductors.b)A.C. potentiometer circuits for dynamic measurements.c) D.C. circuits to give a voltage proportional to velocity for a capacitor.d) Frequency-modulation methods, where the change of C or L varies the frequency of an oscillation circuit.Important features of capacitive and inductive transducers are as follows:i)resolution infiniteii) accuracy+- 0.1% of full scale is quotediii)displacement ranges 25*10-6 m to 10-3miv) rise time less than 50us possibleTypical measurands are displacement, pressure, vibration, sound, and liquid level.8、Linear Variable-differential Ttransformer9、Piezo-electric Transducers10、Electromagnetic Transducers11、Thermoelectric Transducers12、Photoelectric Cells13、Mechanical Transducers and Sensing Elements传感器的基础知识传感器是一种把被测量转换为光的、机械的或者更平常的电信号的装置。
数字温度传感器毕业论文中英文资料外文翻译文献[管理资料]
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毕业论文中英文资料外文翻译文献外文资料DS1722 Digital ThermometerWith scientific and technological progress and development of the types of temperature sensors increasingly wide range of application of the increasingly widespread, and the beginning analog toward digital, single-bus, dual-bus and bus-3 direction. And the number of temperature sensors because they apply to all microprocessor interface consisting of automatic temperature control system simulation can be overcome sensor and microprocessor interface need signal conditioning circuit and A / D converters advant ages of the drawbacks, has been widely used in industrial control, electronic transducers, medical equipment and other temperature control system. Among them, which are more representative of a digital temperature sensor DS18B20, MAX6575, the DS1722, MAX6636 other. This paper introduces the DS1722 digital temperature sensor characteristics, the use of the method and its timing. Internal structure and other relevant content.FEATURES:Temperature measurements require no external components;Measures temperatures from -55°C to +120°C. Fahrenheit equivalent is -67°F to +248°F;Thermometer accuracy is ±°C;Thermometer resolution is configurable from 8 to 12 bits (°C to °C resolution);Data is read from/written to via a Motorola Serial Peripheral Interface (SPI) or standard 3-wire serial interface;Wide analog power supply range ( - );Separate digital supply allows for logic;Available in an 8-pin SOIC (150 mil), 8-pin USOP, and flip chip package;PIN ASSIGNMENTFIGURE 1 PIN ASSIGNMENTPIN DESCRIPTION:SERMODE - Serial Interface Mode.CE - Chip Enable.SCLK - Serial Clock.GND – Ground.VDDA - Analog Supply Voltage.SDO - Serial Data Out.SDI - Serial Data In.VDDD - Digital Supply Voltage.DESCRIPTION:The DS1722 Digital Thermometer and Thermostat with SPI/3-Wire Interface provides temperature readings which indicate the temperature of the device. No additional components are required; the device is truly a temperature-to-digital converter. Temperature readings are communicated from the DS1722 over a Motorola SPI interface or a standard 3-wire serial interface. The choice of interface standard is selectable by the user. For applications that require greater temperature resolution, the user can adjust the readout resolution from 8 to 12 bits. This is particularly useful in applications where thermal runaway conditions must be detected quickly.For application flexibility, the DS1722 features a wide analog supply rail of - . A separate digital supply allows a range of to . The DS1722 is available in an 8-pin SOIC (150-mil), 8-pin USOP, and flip chip package.Applications for the DS1722 include personal computers/servers/workstations, cellular telephones, office equipment, or any thermally-sensitive system.OVERVIEW:A block diagram of the DS1722 is shown in Figure 2. The DS1722 consists offour major components:1. Precision temperature sensor.2. Analog-to-digital converter.3. SPI/3-wire interface electronics.4. Data registers.The factory-calibrated temperature sensor requires no external components. The DS1722 is in a power conserving shutdown state upon power-up. After power-up, the user may alter the configuration register to place the device in a continuous temperature conversion mode or in a one-shot conversion mode. In the continuous conversion mode, the DS1722 continuously converts the temperature and stores the result in the temperature register. As conversions are performed in the background, reading the temperature register does not affect the conversion in progress. In the one-shot temperature conversion mode, the DS1722 will perform one temperature conversion, store the result in the temperature register, and then eturn to the shutdown state. This conversion mode is ideal for power sensitive applications. More information on the configuration register is contained in the “OPERATION-Programming”section. The temperature conversion results will have a default resolution of 9 bits. In applications where small incremental temperature changes are critical, the user can change the conversion resolution from 9 bits to 8, 10, 11, or 12. This is accomplished by programming the configuration register. Each additional bit of resolution approximately doubles the conversion time. The DS1722 can communicate using either a Motorola Serial Peripheral Interface (SPI) or standard 3-wire interface. The user can select either communication standard through the SERMODE pin, tying it to VDDD for SPI and to ground for 3-wire. The device contains both an analog supply voltage and a digital supply voltage (VDDA and VDDD, respectively). The analog supply powers the device for operation while the digital supply provides the top rails for the digital inputs and outputs. The DS1722 was designed to be Logic-Ready.DS1722 FUNCTIONAL BLOCK DIAGRAM Figure 2OPERATION-Measuring Temperature:The core of DS1722 functionality is its direct-to-digital temperature sensor. The DS1722 measures temperature through the use of an on-chip temperature measurement technique with an operating range from -55°to +120°C. The device powers up in a power-conserving shutdown mode. After power-up, the DS1722 may be placed in a continuous conversion mode or in a one-shot conversion mode. In the continuous conversion mode, the device continuously computes the temperature and stores the most recent result in the temperature register at addresses 01h (LSB) and 02h (MSB). In the one-shot conversion mode, the DS1722 performs one temperature conversion and then returns to the shutdown mode, storing temperature in the temperature register. Details on how to change the setting after power up are contained in the “OPERATION-Programming”section. The resolution of the temperature conversion is configurable (8, 9, 10, 11, or 12 bits), with 9-bit readings the default state. This equates to a temperature resolution of °C, °C, °C, °C, or °C. Following each conversion, thermal data is stored in the thermometer register in two’s complement format; the information can be retrieved over the SPI or 3-wire interface with the address set to the temperature register, 01h (LSB) and then 02h (MSB). Table 2 describesthe exact relationship of output data to measured temperature. The table assumes the DS1722 is configured for 12-bit resolution; if the evince is configured in a lower resolution mode, those bits will contain 0s. The data is transmitted serially over the digital interface, MSB first for SPI communication and LSB first for 3-wire communication. The MSB of the temperature register contains the “sign” (S) bit, denoting whether the temperature is positive or negative. For Fahrenheit usage, a lookup table or conversion routine must be used.AddressLocation S 2625242322212002h MSB (unit = ℃) LSB2-12-22-32-40 0 0 0 01hTEMPERATURE DIGITAL OUTPUT(BINARY) DIGITAL OUTPUT(HEX)+120℃0111 1000 0000 0000 7800h+ 0001 1001 0001 0000 1910h+ 0000 1010 0010 0000 0a20h+ 0000 0000 1000 0000 0080h0 0000 0000 0000 0000 0000h1111 1111 1000 0000 Ff80h1111 0101 1110 0000 F5e0h1110 0110 1111 0000 E6f0h-55 1100 1001 0000 0000 C900h OPERATION-Programming:The area of interest in programming the DS1722 is the Configuration register. All programming is done via the SPI or 3-wire communication interface by selecting the appropriate address of the desired register location. Table 3 illustrates the addresses for the two registers (configuration and temperature) of the DS1722.Register Address Structure Table 3CONFIGURATION REGISTER PROGRAMMING:The configuration register is accessed in the DS1722 with the 00h address for reads and the 80h address for writes. Data is read from or written to the configuration register MSB first for SPI communication and LSB first for 3-wire communication. The format of the register is illustrated in Figure 2. The effect each bit has on DS1722 functionality is described below along with the power-up state of the bit. The entire register is volatile, and thus it will power-up in the default state.CONFIGURATION/STATUS REGISTER Figure 21SHOT = One-shot temperature conversion bit. If the SD bit is "1", (continuous temperature conversions are not taking place), a "1" written to the 1SHOT bit will cause the DS1722 to perform one temperature conversion and store the results in the temperature register at addresses 01h (LSB) and 02h (MSB). The bit will clear itself to "0" upon completion of the temperature conversion. The user has read/write access to the 1SHOT bit, although writes to this bit will be ignored if the SD bit is a "0", (continuous conversion mode). The power-up default of the one-shot bit is "0".R0, R1, R2 = Thermometer resolution bits. Table 4 below defines the resolution of the digital thermometer, based on the settings of these 3 bits. There is a direct tradeoff between resolution and conversion time, as depicted in the AC Electrical Characteristics. The user has read/write access to the R2, R1 and R0 bits and the power-up default state is R2="0", R1="0", and R0="1" (9-bit conversions).THERMOMETER RESOLUTION CONFIGURATION Table 4SD = Shutdown bit. If SD is "0", the DS1722 will continuously perform temperature conversions and store the last completed result in the temperature register. If SD is changed to a "1", the conversion in progress will be completed and stored and then the device will revert to a low-power shutdown mode. The communication port remains active. The user has read/write access to the SD bit and the power-up default is "1" (shutdown mode).SERIAL INTERFACE:The DS1722 offers the flexibility to choose between two serial interface modes. The DS1722 can communicate with the SPI interface or with a standard 3-wire interface. The interface method used is determined by the SERMODE pin. When this pin is connected to VDDD SPI communication is selected. When this pin is connected to ground, standard 3-wire communication is selected.SERIAL PERIPHERAL INTERFACE (SPI):The serial peripheral interface (SPI) is a synchronous bus for address and data transfer. The SPI mode of serial communication is selected by tying the SERMODE pin to VDDD. Four pins are used for the SPI. The four pins are the SDO (Serial Data Out), SDI (Serial Data In), CE (Chip Enable), and SCLK (Serial Clock). The DS1722 is the slave device in an SPI application, with the microcontroller being the master. The SDI and SDO pins are the serial data input and output pins for the DS1722, respectively. The CE input is used to initiate and terminate a data transfer. The SCLK pin is used to synchronize data movement between the master (microcontroller) and the slave (DS1722) devices. The shift clock (SCLK), which is generated by the microcontroller, is active only when CE is high and during address and data transfer to any device on the SPI bus. The inactive clock polarity is programmable in somemicrocontrollers. The DS1722 offers an important feature in that the level of the inactive clock is determined by sampling SCLK when CE becomes active. Therefore, either SCLK polarity can be accommodated. There is one clock for each bit transferred. Address and data bits are transferred in groups of eight, MSB first.3-WIRE SERIAL DATA BUS:The 3-wire communication mode operates similar to the SPI mode. However, in 3-wire mode, there is one bi-directional I/O instead of separate data in and data out signals. The 3-wire consists of the I/O (SDI and SDO pins tied together), CE, and SCLK pins. In 3-wire mode, each byte is shifted in LSB first unlike SPI mode where each byte is shifted in MSB first. As is the case with the SPI mode, an address byte is written to the device followed by a single data byte or multiple data bytes.外文资料译文DS1722数字温度传感器随着科学技术的不断进步和发展，温度传感器的种类日益繁多，应用逐渐广泛，并且开始由模拟式向着数字式、单总线式、双总线式和三总线式发展。
传感器中英文介绍
. sensorssensors(English name: transducer/sensor) is a kind of detection device, can feel the measured information, and will feel information transformation according to certain rule become electrical signal output, or other form of information needed to satisfy the information transmission, processing, storage, display, record and control requirements.Sensor's features include: miniaturization, digital, intelligent, multi-functional, systematic and network. It is the first step of automatic detection and automatic control. The existence and development of the sensor, let objects have sensory, such as touch, taste and smell let objects become live up slowly. Usually according to its basic cognitive functions are divided into temperature sensor, light sensor, gas sensor, force sensor, magnetic sensor, moisture sensor, acoustic sensor, radiation sensitive element, color sensor and sensor etc. 10 major categories.temperature transducerTemperature sensors (temperature transducer) refers to can feel temperature translates into usable output signal of the sensor. The temperature sensor is the core part of the temperature measuring instrument, wide variety. According to measuring methods could be divided into two types: contact and non-contact, according to the sensor material and electronic component features divided into two categories, thermal resistance and thermocouple.1 principle of thermocoupleThermocouple is composed of two different materials of metal wire, the welded together at the end. To measure the heating part of the environment temperature, can accurately know the temperature of the hot spots. Because it must have two different material of the conductor, so called the thermocouple. Different material to make the thermocouple used in different temperature range, their sensitivity is also each are not identical. The sensitivity of thermocouple refers to add 1 ℃hot spot temperature changes, the output variation of potential difference. For most of the metal material support thermocouple, this value about between 5 ~ 40 microvolt / ℃.As a result of the thermocouple temperature sensor sensitivity has nothing to do with the thickness of material, use very fine material also can make the temperature sensor. Also due to the production of thermocouple metal materials have good ductility, the slight temperature measuring element has high response speed, can measure the process of rapid change.Its advantages are:(1)high precision measurement. Because of thermocouple direct contact with the object being measured, not affected by intermediate medium.(2)the measurement range. Commonly used thermocouple from 1600 ℃to 50 ℃ ~ + sustainable measurement, some special thermocouple minimum measurable to - 269 ℃ (e.g., gold iron nickel chrome), the highest measurable to + 2800 ℃ (such as tungsten rhenium).(3) simple structure, easy to use. Thermocouple is usually composed of two different kinds of metal wire, but is not limited by the size and the beginning of, outside has protective casing, so very convenient to use. The thermocouple type and structure of the form.2. The thermocouple type and structure formation(1)the types of thermocoupleThe commonly used thermocouple could be divided into two types: standard thermocouple and non-standard thermocouple. Standard thermocouple refers to the national standard specifies its thermoelectric potential and the relationship between temperature, permissible error, and a unified standard score table of thermocouple, it has with matching display instrument to choose from. Rather than a standard thermocouple or on the order of magnitude less than the range to use standardized thermocouple, in general, there is no uniform standard, it is mainly used for measurement of some special occasions.Standardized thermocouple is our country from January 1, 1988, thermocouple and thermal resistance of all production according to IEC international standard, and specify the S, B, E, K, R, J, T seven standardization thermocouple type thermocouple for our country unified design.(2)to ensure that the thermocouple is reliable, steady work, the structure of thermocouple requirements are as follows:①of the two thermocouple thermal electrode welding must be strong;②two hot electrode should be well insulated between each other, in case of short circuit;③compensation wires connected to the free cod of a thermocouple to convenient and reliable;④protect casing thermal electrodes should be able to make sufficient isolation and harmful medium.3.The thermocouple cold end temperature compensationDue to the thermocouple materials are generally more expensive (especiallywhen using precious metals), and the temperature measurement points are generally more far, the distance to the instrument in order to save materials, reduce cost, usually adopt the compensating conductor) (the free end of the cold junction of the thermocouple to the steady control of indoor temperature, connected to the meter terminals. It must be pointed out that the role of the thermocouple compensation wire extension hot electrode, so that only moved to the control room of the cold junction of the thermocouple instrument on the terminal, it itself does not eliminate the cold end temperature change on the influence of temperature, cannot have the compensation effect. So, still need to take some of the other correction method to compensate of the cold end temperature especially when t0 indicates influence on measuring temperature 0 ℃.Must pay attention to when using thermocouple compensating conductor model match, cannot be wrong polarity, compensation conductor should be connected to the thermocouple temperature should not exceed 100 ℃.传感器传感器（英文名称：transducer/sensor）是一种检测装置，能感受到被测量的信息，并能将感受到的信息，按一定规律变换成为电信号或其他所需形式的信息输出，以满足信息的传输、处理、存储、显示、记录和控制等要求。
传感器技术7-热电式传感器-中英对照
第7章 热电式传感器
2.铂、铜热电阻的特性 铂Platinum、铜Copper为应用最广的热电阻材料。 虽然铁Ferrum、镍Nickel的温度系数和电阻率均比 铂、铜要高，但由于存在着不易提纯(purify)和非线 性(nonlinearity)严重的缺点，因而用得不多。 铂容易提纯，在高温和氧化性(oxidative)介质中化 学、物理性能(physical properties)稳定，制成的铂 电阻输出－输入特性接近线性，测量精度高。
E A (T , T0 ) Adt E A (T0 , T )
T0
T
(7-8)
式中 EA(T,T0)——金属A两端温度分别为T与T0时的温差电势； σ A——温差系数(temperature differential coefficient)； T、T0——高、低温端的绝对温度。
第7章 热电式传感器 Thermoelectric Sensors
第7章 热电式传感器
7.1
热电阻传感器 Thermal resistance sensors 热电偶传感器 Thermocouple sensors 热电式传感器的应用 Applications of thermoelectric sensors
第7章 热电式传感器
3.其他热电阻 ⑴.铟(Indium)电阻适宜在-269～-258℃温度范围内使 用，测温精度高，灵敏度是铂电阻的10倍，但是复 现性(repeatability)差。 ⑵.锰(Manganese)电阻适宜在-271～-210℃温度范围 内使用，灵敏度高，但是质脆易损坏。 ⑶.碳(Carbon)电阻适宜在-273～-268.5℃温度范围内 使用，热容量(thermal capacity)小，灵敏度高，价 格低廉，操作简便，但是热稳定性(thermal stability) 较差。
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中英文对照外文翻译文献(文档含英文原文和中文翻译)外文翻译：Thermocouple Temperatur sensorIntroduction to ThermocouplesThe thermocouple is one of the simplest of all sensors. It consists of two wires of dissimilar metals joined near the measurement point. The output is a small voltage measured between the two wires.While appealingly simple in concept, the theory behind the thermocouple is subtle, the basics of which need to be understood for the most effective use of the sensor.Thermocouple theoryA thermocouple circuit has at least two junctions: the measurement junction and a reference junction. Typically, the reference junction is created where the two wires connect to the measuring device. This second junction it is really two junctions: one for each of the two wires, but because they are assumed to be at the same temperature (isothermal) they are considered as one (thermal) junction. It is the point where the metals change - from the thermocouple metals to what ever metals are used in the measuring device - typically copper.The output voltage is related to the temperature difference between the measurement and the reference junctions. This is phenomena is known as the Seebeck effect. (See the Thermocouple Calculator to get a feel for the magnitude of the Seebeck voltage). The Seebeck effect generates a small voltage along the length of a wire, and is greatest where the temperature gradient is greatest. If the circuit is of wire of identical material, then they will generate identical but opposite Seebeck voltages which will cancel. However, if the wire metals are different the Seebeck voltages will be different and will not cancel.In practice the Seebeck voltage is made up of two components: the Peltiervoltage generated at the junctions, plus the Thomson voltage generated in the wires by the temperature gradient.The Peltier voltage is proportional to the temperature of each junction while the Thomson voltage is proportional to the square of the temperature difference between the two junctions. It is the Thomson voltage that accounts for most of the observed voltage and non-linearity in thermocouple response.Each thermocouple type has its characteristic Seebeck voltage curve. The curve is dependent on the metals, their purity, their homogeneity and their crystal structure. In the case of alloys, the ratio of constituents and their distribution in the wire is also important. These potential inhomogeneous characteristics of metal are why thick wire thermocouples can be more accurate in high temperature applications, when the thermocouple metals and their impurities become more mobile by diffusion.The practical considerations of thermocouplesThe above theory of thermocouple operation has important practical implications that are well worth understanding:1. A third metal may be introduced into a thermocouple circuit and have no impact, provided that both ends are at the same temperature. This means that the thermocouple measurement junction may be soldered, brazed or welded without affecting the thermocouple's calibration, as long as there is no net temperature gradient along the third metal.Further, if the measuring circuit metal (usually copper) is different to that of the thermocouple, then provided the temperature of the two connecting terminals is the same and known, the reading will not be affected by the presence of copper.2. The thermocouple's output is generated by the temperature gradient along the wires and not at the junctions as is commonly believed. Therefore it is important that the quality of the wire be maintained where temperature gradients exists. Wire quality can be compromised by contamination from its operating environment and the insulating material. For temperatures below 400°C, contamination of insulated wires is generally not a problem. At temperatures above 1000°C, the choice of insulationand sheath materials, as well as the wire thickness, become critical to the calibration stability of the thermocouple.The fact that a thermocouple's output is not generated at the junction should redirect attention to other potential problem areas.3. The voltage generated by a thermocouple is a function of the temperature difference between the measurement and reference junctions. Traditionally the reference junction was held at 0°C by an ice bath:The ice bath is now considered impractical and is replace by a reference junction compensation arrangement. This can be accomplished by measuring the reference junction temperature with an alternate temperature sensor (typically an RTD or thermistor) and applying a correcting voltage to the measured thermocouple voltage before scaling to temperature.The correction can be done electrically in hardware or mathematically in software. The software method is preferred as it is universal to all thermocouple types (provided the characteristics are known) and it allows for the correction of the small non-linearity over the reference temperature range.4. The low-level output from thermocouples (typically 50mV full scale) requires that care be taken to avoid electrical interference from motors, power cable, transformers and radio signal pickup. Twisting the thermocouple wire pair (say 1 twist per 10 cm) can greatly reduce magnetic field pickup. Using shielded cable or running wires in metal conduit can reduce electric field pickup. The measuring device should provide signal filtering, either in hardware or by software, with strong rejection of the line frequency (50/60 Hz) and its harmonics.5. The operating environment of the thermocouple needs to be considered. Exposure to oxidizing or reducing atmospheres at high temperature can significantly degrade some thermocouples. Thermocouples containing rhodium (B,R and S types) are not suitable under neutron radiation.The advantages and disadvantages of thermocouplesBecause of their physical characteristics, thermocouples are the preferred methodof temperature measurement in many applications. They can be very rugged, are immune to shock and vibration, are useful over a wide temperature range, are simple to manufactured, require no excitation power, there is no self heating and they can be made very small. No other temperature sensor provides this degree of versatility.Thermocouples are wonderful sensors to experiment with because of their robustness, wide temperature range and unique properties.On the down side, the thermocouple produces a relative low output signal that is non-linear. These characteristics require a sensitive and stable measuring device that is able provide reference junction compensation and linearization.Also the low signal level demands that a higher level of care be taken when installing to minimise potential noise sources.The measuring hardware requires good noise rejection capability. Ground loops can be a problem with non-isolated systems, unless the common mode range and rejection is adequate.Types of thermocoupleAbout 13 'standard' thermocouple types are commonly used. Eight have been given an internationally recognised letter type designators. The letter type designator refers to the emf table, not the composition of the metals - so any thermocouple that matches the emf table within the defined tolerances may receive that table's letter designator.Some of the non-recognised thermocouples may excel in particular niche applications and have gained a degree of acceptance for this reason, as well as due to effective marketing by the alloy manufacturer. Some of these have been given letter type designators by their manufacturers that have been partially accepted by industry.Each thermocouple type has characteristics that can be matched to applications. Industry generally prefers K and N types because of their suitability to high temperatures, while others often prefer the T type due to its sensitivity, low cost and ease of use.A table of standard thermocouple types is presented below. The table also showsthe temperature range for extension grade wire in brackets.Accuracy of thermocouplesThermocouples will function over a wide temperature range - from near absolute zero to their melting point, however they are normally only characterized over their stable range. Thermocouple accuracy is a difficult subject due to a range of factors. In principal and in practice a thermocouple can achieve excellent results (that is, significantly better than the above table indicates) if calibrated, used well below its nominal upper temperature limit and if protected from harsh atmospheres. At higher temperatures it is often better to use a heavier gauge of wire in order to maintain stability (Wire Gauge below).As mentioned previously, the temperature and voltage scales were redefined in 1990. The eight main thermocouple types - B, E, J, K, N, R, S and T - were re-characterised in 1993 to reflect the scale changes. (See: NIST Monograph 175 for details). The remaining types: C, D, G, L, M, P and U appear to have been informally re-characterised.Try the thermocouple calculator. It allows you the determine the temperature by knowing the measured voltage and the reference junction temperature.Thermocouple wire gradesThere are different grades of thermocouple wire. The principal divisions are between measurement grades and extension grades. The measurement grade has the highest purity and should be used where the temperature gradient is significant. The standard measurement grade (Class 2) is most commonly used. Special measurement grades (Class 1) are available with accuracy about twice the standard measurement grades.The extension thermocouple wire grades are designed for connecting the thermocouple to the measuring device. The extension wire may be of different metals to the measurement grade, but are chosen to have a matching response over a much reduced temperature range - typically -40°C to 120°C. The reason for using extension wire is reduced cost - they can be 20% to 30% of the cost of equivalent measurementgrades. Further cost savings are possible by using thinnergauge extension wire and a lower temperature rated insulation.Note: When temperatures within the extension wire's rating are being measured, it is OK to use the extension wire for the entire circuit. This is frequently done with T type extension wire, which is accurate over the -60 to 100°C range.Thermocouple wire gaugeAt high temperatures, thermocouple wire can under go irreversible changes in the form of modified crystal structure, selective migration of alloy components and chemical changes originating from the surface metal reacting to the surrounding environment. With some types, mechanical stress and cycling can also induce changes.Increasing the diameter of the wire where it is exposed to the high temperatures can reduce the impact of these effects.The following table can be used as a very approximate guide to wire gauge:At these higher temperatures, the thermocouple wire should be protected as much as possible from hostile gases. Reducing or oxidizing gases can corrode some thermocouple wire very quickly. Remember, the purity of the thermocouple wire is most important where the temperature gradients are greatest. It is with this part of the thermocouple wiring where the most care must be taken.Other sources of wire contamination include the mineral packing material and the protective metal sheath. Metallic vapour diffusion can be significant problem at high temperatures. Platinum wires should only be used inside a nonmetallic sheath, such as high-purity alumna.Neutron radiation (as in a nuclear reactor) can have significant permanent impact on the thermocouple calibration. This is due to the transformation of metals to different elements.High temperature measurement is very difficult in some situations. In preference, use non-contact methods. However this is not always possible, as the site of temperature measurement is not always visible to these types of sensors.Colour coding of thermocouple wireThe colour coding of thermocouple wire is something of a nightmare! There are at least seven different standards. There are some inconsistencies between standards, which seem to have been designed to confuse. For example the colour red in the USA standard is always used for the negative lead, while in German and Japanese standards it is always the positive lead. The British, French and International standards avoid the use of red entirely!Thermocouple mountingThere are four common ways in which thermocouples are mounted with in a stainless steel or Inconel sheath and electrically insulated with mineral oxides. Each of the methods has its advantages and disadvantages.Sealed and Isolated from Sheath: Good relatively trouble-free arrangement. The principal reason for not using this arrangement for all applications is its sluggish response time - the typical time constant is 75 secondsSealed and Grounded to Sheath: Can cause ground loops and other noise injection, but provides a reasonable time constant (40 seconds) and a sealed enclosure.Exposed Bead: Faster response time constant (typically 15 seconds), but lacks mechanical and chemical protection, and electrical isolation from material being measured. The porous insulating mineral oxides must be sealedExposed Fast Response: Fastest response time constant, typically 2 seconds but with fine gauge of junction wire the time constant can be 10-100 ms. In addition to problems of the exposed bead type, the protruding and light construction makes the thermocouple more prone to physical damage.Thermocouple compensation and linearizationAs mentioned above, it is possible to provide reference junction compensation in hardware or in software. The principal is the same in both cases: adding a correction voltage to the thermocouple output voltage, proportional to the reference junction temperature. To this end, the connection point of the thermocouple wires to the measuring device (i.e. where the thermocouple materials change to the copper of thecircuit electronics) must be monitored by a sensor. This area must be design to be isothermal, so that the sensor accurately tracks both reference junction temperatures.The hardware solution is simple but not always as easy to implement as one might expect.The circuit needs to be designed for a specific thermocouple type and hence lacks the flexibility of the software approach.The software compensation technique simplifies the hardware requirement, by eliminating the reference sensor amplifier and summing circuit (although a multiplexer may be required).The software algorithm to process the signals needs to be carefully written. A sample algorithm details the process.A good resource for thermocouple emf tables and coefficients is at the US Commerce Dept's NIST web site. It covers the B, E, J, K, N, R, S and T types.The thermocouple as a heat pumpThe thermocouple can function in reverse. If a current is passed through a thermocouple circuit, one junction will cool and the other warm. This is known as the Peltier Effect and is used in small cooling systems. The effect can be demonstrated by alternately passing a current through a thermocouple circuit and then quickly measuring the circuit's Seebeck voltage. This process has been used, with very fine thermocouple wire (0.025 mm with about a 10 mA current), to measure humidity by ensuring the cooled junction drops below the air's dew point. This causes condensation to form on the cooled junction. The junction is allowed to return to ambient, with the temperature curve showing an inflection at the dew point caused by the latent heat of vaporization.Measuring temperature differencesThermocouples are excellent for measuring temperatures differences, such as the wet bulb depression in measuring humidity. Sensitivity can be enhanced by constructing a thermopile - a number of thermocouple circuits in series.In the above example, the thermopile output is proportional to the temperaturedifference T1 - T2, with a sensitivity three times that of a single junction pair. In practice, thermopiles with two to hundreds of junctions are used in radiometers, heat flux sensors, flow sensors and humidity sensors. The thermocouple materials can be in wire form, but also printed or etched as foils and even electroplated.An excellent example of the thermopile is in the heat flux sensors manufactured by Hukseflux Thermal Sensors. Also see RdF Corp. and Exergen Corp.The thermocouple is unique in its ability to directly measure a temperature difference. Other sensor types require a pair of closely matched sensors to ensure tracking over the entire operational temperature range.The thermoelectric generatorWhile the Seebeck voltage is very small (in the order of 10-70μV/°C), if the circuit's electrical resistance is low (thick, short wires), then large currents are possible (e.g. many amperes). An efficiency trade-off of electrical resistance (as small as possible) and thermal resistance (as large as possible) between the junctions is the major issue. Generally, electrical and thermal resistances trend together with different materials. The output voltage can be increased by wiring as a thermopile.The thermoelectric generator has found its best-known application as the power source in some spacecraft. A radioactive material, such as plutonium, generates heat and cooling is provided by heat radiation into space. Such an atomic power source can reliably provide many tens of watts of power for years. The fact that atomic generators are highly radioactive prevents their wider application.译文：热电偶温度传感器热电偶的定义热电偶是最简单的传感器之一。