熱敏電阻介紹

1、熱敏電阻介紹Concept Definition:Thermistor: thermally sensitive resistor Application:Temperature Detector, Control, Switch, Fuse Catalog: NTC,PTC, RTD,NTC: Negative Temperature Coefficient ResistorPTC: Positive Temperature Coefficient ResistorRTD: Resistance Temperature Detector Resistance Temperature Dete

2、ctorType Element Material Base Resistance (Ohms) TCR (Ohm/Ohm/C) Base Resistance Tolerance +/- TCR Tolerance % CB COPPER 10 OHMS AT 25C .00427 0.2% 1% CC COPPER 10 OHMS AT 25C .00427 0.5% 1% NA NICKEL 120 OHMS AT 0C .00672 0.5% 1% PA PLATINUM 100 OHMS AT 0C .00385 0.06% 0.12% PB PLATINUM 100 OHMS AT

3、 0C .00385 0.12% 0.35% PC PLATINUM 100 OHMS AT 0C .00385 0.5% 1% PE PLATINUM 100 OHMS AT 0C .00391 0.12% 0.35% PF PLATINUM 100 OHMS AT 0C .00391 0.5% 1% PG PLATINUM 100 OHMS AT 0C .00375 0.12% 0.35% PH PLATINUM 100 OHMS AT 0C .00392 0.5% 0.1% Type: Wire Wound, Thin FilmMaterial: Pt, Cu, NiPrinciple:

4、 R- T effectSample: see photosTypical performance: See below tableFeatures: accuracy, linearResistance Temperature DetectorFeaturesRtdThermocoupleAccuracyMore AccurateLess AccurateTemperature Range-200 to 600C-200 to 2000CInitial CostMore ExpensiveLess ExpensiveSensitivity1 Typical (other lengths av

5、ailable)Point Sensing OnlyResponse Time1 to 7 secondsless than 0.1 secondRobustnessGoodGood, Subject to driftReference JunctionNot RequiredRequiredLong Term StabilityExcellentGood. Subject to driftOutputResistance0.4 ohm/ohm/CHighly LinearVoltage10-40 microvolts/C,Approximately linearElectrical Nois

6、eResistanceLess susceptibleMore susceptibleResistance Temperature Detector (Rtd) vs. Thermocouples (General Principles)ThermocoupleType: K, E, J, N ,B, R, SMaterial: Pt Rhodium, W- Rhenium, Constantan, CupronPrinciple: Seebeck effect that the junction between two metals generates a voltage which is

7、a function of temperatureTypical performance: See below tableFeatures: interchangeable, wide range of temperaturesThermocouple typeOverall range CsensitivityB(Platinum / Rhodium)20 to 182010 V/CE(Chromel / Constantan)-270 to 91068 V/CJ (Iron / Constantan)-210 to 120050 V/CK(Chromel / Alumel)-270 to

8、137041 V/CN(Nicrosil / Nisil)-270 to 130010 V/CR(Platinum / Rhodium)-50 to 176010 V/CS(Platinum / Rhodium)-50 to 176010 V/CT(Copper/Constantan)-270 to 40060 V/CDeg C 0 2 4 6 8 -20 -0.995 -1.093 -1.19 -1.288 -1.385 -10 -0.501 -0.6 -0.699 -0.798 -0.896 0 0 -0.101 -0.201 -0.301 -0.401 Deg C 0 2 4 6 8 0

9、 0 0.101 0.202 0.303 0.405 10 0.507 0.609 0.711 0.813 0.916 20 1.019 1.122 1.225 1.329 1.432 Type J : V (mV) / T (C) TableNTCType: disc, rod, chipMaterial: Ceramic (Mn, Fe, Co, Ni, Zn etc, transition metal oxides)Principle: R-T effectSamples: See photo: Epoxy and Glass PKG.Typical performance: See b

10、elow tableFeatures: Cheap, high sensitivity, small sizeNTC ParameterZero-Power Resistance (R0) : R0 is the measured DC(direct current) resistance at a specific temperature T when the power dissipation is negligible. Generally consider the power to be negligible when any decrease in power will result

11、 in not more than a 0.1% change in resistance.Alpha () (Temperature coefficient): Alpha, a material characteristic, is defined as the percentage resistance change per degree centigrade. For NTC thermistor, typical value of alpha are in the range of -3%C to -6%C.Beta value (): B value can be regarded

12、 a quantitative value of thermistor materials that is assigned as a material constant and that indicates the relationship of material resistivity to temperature.NTC Steinhart Equation (R-T Relationship) Experiential Formula: , , NTC ParameterTolerance : Tolerance for thermistor is the specified resi

13、stance percentage or temperature deviation from curve nominal values.Thermal Time Constant: It is the time required for a thermistor to change its body temperature by 63.2% of a specified temperature span when the measurement are made under zero-power conditions in thermally stable environment.Therm

14、al Dissipation Constant: It is defined as the power required to raise the thermistors body temperature by 1C in a particular measurement medium. Its units is expressed in the unit of mw/C.Rating Power: It is specified as the required power that thermistor are heated up by 100C at 25C.= W/（T-Ta） = I