1、无 锡 职 业 技 术 学 院 毕业设计说明书（英文翻译） 2 英文翻译 Temperature humidity sensor The 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
2、process march, regardless of in the industry, the agriculture, the scientific research, the national defense and peoples 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
3、 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 temper
4、ature sensor material and the principle of work to tie the type thermoelectricity type radiation formula r 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 electrica
5、l 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 w
6、hich 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 10
7、8 m, therefore is the insulator. If carries on the doping in BaTio3, may cause the BaTio3 semiconductor, for example: Mixes by 0.1%-0.3% rare-earth element, but causes it to become has 0.1 under the normal temperature-10 m N line of semiconductors .Has electricity semiconductor BaTio3, when the temp
8、erature achieved when Curie temperature T, it transforms by the tetragonal system into the cubic system, this time its electronic resistivity leap increases several magnitudes (103-107 times).Positive temperature coefficient the (PTC) acts according to this nature manufacture. After in semiconductor
9、 multi-crystal grain structure BaTio3, its crystal grain (general size small is approximately 3-10 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-
10、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 tetr
11、agonal 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 boundary potential barrier is easy. But above Curie temperature T c, BaTio3 becomes the cubic system by the tetragonal s
12、ystem, 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 barrie
13、r as shown in Figure 3-2.b is potential barrier level thickness, 0 is the barrier height .According to the equation, the barrier height 0 sticks the effective dielectric constant e ff between with the crystal the relations is: In the formula, n0 is the density of donors； e is the electronic electric
14、 quantity .0 is the vacuum coefficient of d i electrical loss. When the electronic overstepping potential barrier enters 0, the electronic resistivity may write is When the temperature is lower than Curie temperature TC, e ff the value is 无 锡 职 业 技 术 学 院 毕业设计说明书（英文翻译） 3 approximately about 104, ther
15、efore 0 very small, the ceramic electronic resistivity rho approaches in the volume resistivity v, 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 l
16、ike 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 characteristi
17、c .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. Thu
18、s 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
19、, 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
20、； 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 =0eEi/KT Obviously the metal oxide compound semiconductor e
21、lectronic 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 negat
22、ive 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 a resistance number point of discontinuity, approximately for 68 , resistance number point of di
23、scontinuity magnitude generally in 37.May 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
24、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. 3.2 temperature sensor basic characteristic in view of the fact that the temperature sensor type is many, moreover its work mechanism is also differ
25、ent. This mainly introduces t the hot sensitive diode and the hot sensitive transistor characteristic and the parameter. 3.2.1 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, tu
26、bular, 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), swit
27、ch 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 resistanc
28、e 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 tempera
29、ture 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 无 锡 职 业 技 术 学 院 毕业设计说明书（英文翻译） 4 resistance number expressed with RT. Is under certain ambient temperature, uses causes
30、the resistance number change not to surpass the resistance value which 0.1% 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 resis
31、tor 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
32、, usually takes the ambient temperature for 25 to take the reference temperature, then has: NTC puts the resistor hotly: RT/R25=expB(1/T-1/298) PTC g change along with the temperature T change, and is proportional with material constant B. Therefore, usually while gives the resistance temperature co
33、efficient, 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 0.5%/ 110%/ between. But the switch (mutant) positive temperature co efficient T may achieve 60%/ or higher. Material
34、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 resisti
35、vity 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 resis
36、tor, 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 use
37、s 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 velocit
38、y 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. Whe
39、n 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 o
40、f 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 r
41、efers 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 paraphra
42、se 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
43、 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
