【正文】 , 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(TT0)△ 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 pound semiconductor ceramics wet sensitive resistor, for example: MgCr2O4 series, ZnOCr2O3 series。 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: 0NeEi/kT If mand, then type changes: rho =ρ0eEi/KT Obviously the metal oxide pound 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 44. In the chart the anti r curve has a resistance 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 onoff 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 pound like C a O, B a O, S O or P2O5, TiO2 bees 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, rodshaped, 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)。0 very small, the ceramic electronic resistivity rho approaches in the volume resistivity ρ 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 like chart .NTC t h r principle of work NTC the r s tor majority is by the transition family metal oxide pound (mainly is with M n, co, Ni, Fe and so on), the agglutination forms the semiconductor metal oxide pound under the controlled condition, they only have the P semiconductor characteristic .Regarding the mon semiconducting material, the electronic resistivity mainly is relies on alo