Temperature Measurements

Size: px

Start display at page:

Download "Temperature Measurements"

Sheila Simpson
5 years ago
Views:

1 DR. GYURCSEK ISTVÁN Temperature Measurements Sources and additional materials (recommended) Lambert Miklós: Szenzorok elmélet (ISBN ) Bp Jacob Fraden: Handbook of Modern Sensors (ISBN ) Springer NY S. Tumanski:Principles of electrical measurement, CRC Press ISBN Máté J.: Méréstechnika 1. PTE PMMIK, ERFP-DD2001-HU-B-01 Dr. Petróczky Károly: Bevezetés a nyúlásmérő bélyeges méréstechnikába, SZIE,Gödöllő 1 gyurcsek.istvan@mik.pte.hu

2 Sensor Groups (THERM,EL,X) (RAD,EL,X) (MECH,EL,X) (MAG,EL,X) (CHEM,EL,X) Metal Resistors Photometers Force, Torque, Pressure Magnetoresistors Elecrochemistry Semiconductor NTC,PTC,pn Radiowave Detectors Position Detectors Galvanic- Magnetic Det. Humidity Detectors Thermocouples IR Sensors Flow Sensors Ionselective Detectors Thermal Switches Quant Detectors Speed Sensors Gas Detectors Accelerometers Acoustic Detectors 2 gyurcsek.istvan@mik.pte.hu

3 Thermal Sensors (therm,el,x) Principles of operation Thermal conductivity (contact sensors) Thermal radiation (pyrometers) Groups Passive R = R(T) Active V = V(T) RTD sensors (therm,el,el) o Pt or Ni RTD (Resistance Temp. Detector) Semiconductors (therm, el, el) o NTC / PTC thermistors o PN - junction sensors (diodes) Thermocouples (therm,el,0) 3 gyurcsek.istvan@mik.pte.hu

4 Resistance Temperature Detectors Thermistors NTC Thermistors PTC Thermiszors PN - Junction Sensors Thermocouples Pyrometers 4 gyurcsek.istvan@mik.pte.hu

Resistance Resistance Temperature Detectors RTD metal resistance sensor R θ R 0 1 + θ rough estimation because = (θ) where θ = t 0 Pt-100 [lower sensitivity], [higher measuring range], [world

5 Resistance Resistance Temperature Detectors RTD metal resistance sensor R θ R θ rough estimation because = (θ) where θ = t 0 Pt-100 [lower sensitivity], [higher measuring range], [world standard essentially] Static characteristics (polynomial) R θ θ θ 2 Ω, 0 ϑ < 850 R θ θ θ θ 100 θ 3 Ω, 200 ϑ < 0 Ni-100 [better sensitivity], [lower measuring range] Static characteristics R θ θ θ θ 4 Ω, 60 ϑ < 180 Semiconductor (not RTD) Nickel Copper Platinum Temperature RTD = (therm,el,el) 5 gyurcsek.istvan@mik.pte.hu

6 Resistance Temperature Detectors Thermistors NTC Thermistors PTC Thermiszors PN - Junction Sensors Thermocouples Pyrometers 6 gyurcsek.istvan@mik.pte.hu

Thermistors in General Semiconductor based passive sensors Periodic

7 Thermistors in General Semiconductor based passive sensors Periodic system, IV. main group metal oxides (Cr, Mn, Fe Co Ni, ) NTC NiO-MnO-CoO, Cu 2 O-MnO, Cu 2 O-ZnO, PTC titanium alloy Construction low heat capacity! (examples) chip thermistor glass flat chopper Bead thermistor (gyöngy) Dial thermistor (tárcsa) Rod thermistor (rúd) Chip thermistor (morzsa) lacker 7 gyurcsek.istvan@mik.pte.hu

8 NTC Thermistors (therm,el,el) R T = R(T 0 ) e B 1 T 1 T 0 PARAMETERS B (material constant) K R(T 0 ) ( cold resistance) 10 kω R = αr T α = 1 R R T = B T 2 S = R T = B T 2 R lower temp higher sensitivity 8 gyurcsek.istvan@mik.pte.hu

Applications o Overcurrent (voltage) protection (instead of fuse) o

9 PTC Thermistor (therm,el,el) Semiconductors barium titanate (BaTiO 3 ) Much better sensitivity than RTD Static characteristics 3 regions Applications o Overcurrent (voltage) protection (instead of fuse) o Temperature compensation (oscillators) 9 gyurcsek.istvan@mik.pte.hu

Thermistor Applications (1) Temperature Measurement Potential divider circuit

increase current increase Prevention appropriate R S R S - R TH order (V OUT = V

R TH - R S order (V OUT = V S ) o The hotter the thermistor, the higher the

10 Thermistor Applications (1) Temperature Measurement Potential divider circuit Bridge circuit Danger Thermal runaway o I 2. R temp. increase current increase Prevention appropriate R S R S - R TH order (V OUT = V TH ) o The hotter the thermistor, the lower the voltage. R TH - R S order (V OUT = V S ) o The hotter the thermistor, the higher the voltage. Amplifier o Differential amplifier for high sensitivity o Schmitt-trigger circuit for ON-OFF switching 10 gyurcsek.istvan@mik.pte.hu

11 Thermistor Applications (2) Inrush Current Limiter (ICL)

12 Resistance Temperature Detectors Thermistors NTC Thermistors PTC Thermiszors PN - Junction Sensors Thermocouples Pyrometers 12 gyurcsek.istvan@mik.pte.hu

13 PN-junction Temp Detectors Drawback in ELECTRONICS temperature-dependent characteristics Forward characteristics (Si diode) shifts to the left at the rate of -2.5 mv/ o C Reverse characteristics (Si and Ge diode) reverse saturation current doubles for every 10 o C rise in temperature 13 gyurcsek.istvan@mik.pte.hu

14 PN-junction Temp Detectors Source: ConceptsElectronics.com Source: ConceptsElectronics.com

15 Resistance Temperature Detectors Thermistors NTC Thermistors PTC Thermiszors PN - Junction Sensors Thermocouples Pyrometers 15 gyurcsek.istvan@mik.pte.hu

Thermocouples (therm,el,0) Principle of operation temp. dept. contact potential V = kt Temperature ( o C) V Fe-CuNi (mv) V NiCr-Ni (mv) -200-8.15-100 -4.75 0 0 0 100 5.37 4.10 200 10.95 8.13 300 16.

16 Thermocouples (therm,el,0) Principle of operation temp. dept. contact potential V = kt Temperature ( o C) V Fe-CuNi (mv) V NiCr-Ni (mv) V sen V ref1 V ref2 = k sen T sen = k ref1 T ref = k ref2 T ref V meter = V sen V ref1 V ref2 V meter = k sen T sen (k ref1 k ref2 )T ref = k sen T sen k ref T ref gyurcsek.istvan@mik.pte.hu

17 Cold Point Compensation

18 Resistance Temperature Detectors Thermistors NTC Thermistors PTC Thermiszors PN - Junction Sensors Thermocouples Pyrometers 18 gyurcsek.istvan@mik.pte.hu

building diagnostics Moisture diagnostics ( )

19 Principle of Pyrometry (rad,el,x) Radiation-based temperature measurement. (optical system is excluded) Thermal imaging (advanced diagnostic solutions) Thermal building diagnostics Moisture diagnostics ( ) Medicine diagnostics ( ) 19 gyurcsek.istvan@mik.pte.hu

20 Questions