Infrared Thermometers - Saba Web Pagesaba.kntu.ac.ir/eecd/ecourses/inst 86/Projects/Infrared...
Transcript of Infrared Thermometers - Saba Web Pagesaba.kntu.ac.ir/eecd/ecourses/inst 86/Projects/Infrared...
InfraredInfraredThermometersThermometers
Supervisor: Prof. H. Taghirad
Produced by: Mahya Shahbazi
K. N. Toosi University of Tech
Introduction Theory ConstructionClassificationApplicationConditioning CircuitsError in MeasurementSmart Pyrometers
What is Infrared?
• Wavelength range : 0.7-1000 micron• Wavelength range used in IR Thermometers :0.7-14
Infrared and vision in Animals!
• The ability of bats and dolphins to "see" with sonar
• specialized organs near vipers’ eyes to sense the infrared radiation
Why Infrared Thermometers?!
Measuring the temperature of hot & moving targets. Not to require contact with the target, then no interface with or damage the objectNot to remove heat or disturb the processthe only solution when the product is small, fragile or in a vacuum or controlled atmosphere
Stefan Boltzmann
4Tw σ=
• Wien Planck :When the detector is used in specific range
λελλ λ dCJd TC /51
2−−=
We can do the classification in two ways.
First Classification:
Narrow band thermometers Broadband thermometers Band-pass thermometers
Second Classification:
Ratio thermometersOptical pyrometersAcoustic Pyrometers (For gas temperatures) Imaging pyrometers
Narrow-Band Thermometers
Narrow band wavelengths (For example: Thermometers with silicon detector, wavelengths: 0.9 - 1.1 micro)Accuracy: 0.25 - 2%Using “Filter” to be narrow bandHigh Accuracy when choosing narrow-bands (For example the bandwidth of 8 – 14 suitable for avoiding the humidity interference or the bandwidth of about 3.6m to avoid the CO2 interference ) Coverage of narrow range of temperatures
Broad Band Thermometers
Wide Range of wavelengths: 0.3 – 20 micronTotal Radiation thermometer
Sensitive to smoke, vapor and other emissivity absorbing gases
Needing to have a clean optical system
Economical because of low price and wide range of measurement
Band Pass Thermometers
Broad band Thermometers with some changes in optical systems
Suitable for a special range of wavelengths (For example one with range of .02 – 5 m useful for glass industry )
Doing so weak when using in another range
Optical Pyrometers
Narrow band measurementvisible Wavelengths (Red & Yellow)Single color thermometer (Red and Yellow)
Optical Pyrometers
Narrow band measurementvisible Wavelengths (Red & Yellow)Single color thermometer (Red and Yellow)Disappearing Filament Thermometer
Optical Pyrometers
Narrow band measurementvisible Wavelengths (Red & Yellow)Single color thermometer (Red and Yellow)Disappearing Filament ThermometerAccuracy of 1 – 2%Rheostat-typeWedge-type
Ratio ThermometersTwo color PyrometerNot sensitive to changes in target's parameters, effect of vapor and other absorbing gases and somehow differential!Multi-wavelengths ThermometerHigh accuracy(0.5 – 2%) and repeatability
Acoustic PyrometersGas temperature measurementGas temperature and the sonic speedFlight time
MrRT
tdc ==
Imaging Pyrometers
A combination of “video & signal processing” and “Pyrometry”2Dimentional picture with false color
MirrorsIndependency between Reflectivity and wavelength in Industrial rangeCopper, silver and goldShould be protected against tarnish by a protective filmGenerally used in fixed focus optical instruments
LensesEasier to be used in varying focus optical instruments rather than mirrors
WindowSo effective on the band of wavelengths (For example Glass does not transmit well beyond 2.5 microns)
Thermal Detectors
Changes in resistance and voltage by receiving radiation Thermopile: consists of multiple thermocouples in series Bolometer: resistance thermometers arranged for response to radiationbroadband detectorsrelatively slow and having time constants of a second or more.less sensitive than other types
Quantum Detectors
Are directly excited by photon in the infrared rangePhotoconductive: Exhibit increased conductivity with received radiation. Photovoltaic: Convert received radiation into electric current. Have a sensitivity 1000 to 100,000 times that of the thermal detectorResponse time about microsecond
Pyroelectric Detectors
Changing in surface charge in response to received radiation.
No need to reach thermal equilibrium when the target temperature changes despite two other types.
The detector change can be likened to a change in charge of a capacitor
allowing bidirectional, serial communications between sensors on the manufacturing floor and computers in the control roomThe smaller sensor so easier installation in tight or awkward areas. No need to shut down the process when some setting is needed No need to buy a new unit and calibrate it or remove the sensor to upgrade the itEasily changing the sensor parameters from a remote P.C.Being able to active an alarm when it fails
Fever measurement in human (ear thermometers )Electrical systemsGlass mold temperatureFood IndustryBuilding science