8/6/2019 13 - Non-Contact Temp Measurement 2011
1/16
NonNon--Contact TemperatureContact TemperatureMeasurementMeasurement
Pyrometer systemsPyrometer systems Optical pyrometerOptical pyrometer
Radiation pyrometerRadiation pyrometer
Infrared ThermocoupleInfrared Thermocouple
8/6/2019 13 - Non-Contact Temp Measurement 2011
2/16
The PyrometerThe Pyrometer
One of the methods or heat transmission isOne of the methods or heat transmission iselectromagnetic radiationelectromagnetic radiation
A Pyrometer measures the electromagneticA Pyrometer measures the electromagnetic
radiation emitted by a body.radiation emitted by a body. A body will radiate heat if its temperature is higherA body will radiate heat if its temperature is higher
than the ambient temperature.than the ambient temperature.
The amount of radiation emitted is based on notThe amount of radiation emitted is based on not
just heat but on two things:just heat but on two things:1.1. The temperature of the bodyThe temperature of the body2.2. The body's ability to send radiation, or its emittanceThe body's ability to send radiation, or its emittance
A body will emit both visible and infrared radiationA body will emit both visible and infrared radiation
8/6/2019 13 - Non-Contact Temp Measurement 2011
3/16
The Optical PyrometerThe Optical Pyrometer
Also referred to as Narrowband pyrometers.Also referred to as Narrowband pyrometers.
Used in the visible light spectrum onlyUsed in the visible light spectrum only
Matches the colour of a lamp filament to the colourMatches the colour of a lamp filament to the colour
of the object to be measuredof the object to be measured By matching the colours, the temperature of theBy matching the colours, the temperature of the
body can be determined.body can be determined.
Requires human to view and set the filament colourRequires human to view and set the filament colour
8/6/2019 13 - Non-Contact Temp Measurement 2011
4/16
Optical Pyrometer OperationOptical Pyrometer Operation
While viewing theWhile viewing thefilament, current isfilament, current isadjusted until theadjusted until thefilament matches thefilament matches thetarget colourtarget colour
Temperature is thenTemperature is thenread from theread from thecalibrated rheostat.calibrated rheostat.
8/6/2019 13 - Non-Contact Temp Measurement 2011
5/16
Radiation PyrometerRadiation Pyrometer
Also known as broadband pyrometerAlso known as broadband pyrometer
Responds to both the visible light andResponds to both the visible light and
the infrared radiation spectrumthe infrared radiation spectrum Based on a relationship betweenBased on a relationship between
radiation emission and temperatureradiation emission and temperature
8/6/2019 13 - Non-Contact Temp Measurement 2011
6/16
Lens Collector PyrometerLens Collector Pyrometer
8/6/2019 13 - Non-Contact Temp Measurement 2011
7/16
Mirror Collector PyrometerMirror Collector Pyrometer
8/6/2019 13 - Non-Contact Temp Measurement 2011
8/16
Handheld IR PyrometerHandheld IR Pyrometer
A couple of examples from OmegaA couple of examples from Omega
8/6/2019 13 - Non-Contact Temp Measurement 2011
9/16
Radiation Pyrometers useRadiation Pyrometers use
ThermopilesThermopiles A thermopile is a densely packed groupA thermopile is a densely packed group
of thermocouples that are connected inof thermocouples that are connected in
seriesseries The radiation from the heat source isThe radiation from the heat source is
concentrated by a lens or concaveconcentrated by a lens or concave
mirror onto the thermopile whichmirror onto the thermopile which
produces a voltage output based on theproduces a voltage output based on theradiation.radiation.
8/6/2019 13 - Non-Contact Temp Measurement 2011
10/16
Thermopile examplesThermopile examples
Thermopile
Receiving
Element
Output
Leads
Hot
Junctions
ColdJunctions
8/6/2019 13 - Non-Contact Temp Measurement 2011
11/16
EmissivityEmissivity
The radiant energy emitted by a body dependsThe radiant energy emitted by a body dependson other things besides heaton other things besides heat
Factors that effect a bodys emissivity include:Factors that effect a bodys emissivity include:
Surface roughness, MaterialSurface roughness, Material
Shape, colourShape, colour
Emissivity is defined as the ratio of the energyEmissivity is defined as the ratio of the energy
radiated by an object at a given temperature toradiated by an object at a given temperature to
the energy emitted by a perfect radiator, orthe energy emitted by a perfect radiator, orblackbody, at the same temperature.blackbody, at the same temperature.
The emissivity of a blackbody is 1.0. All valuesThe emissivity of a blackbody is 1.0. All valuesof emissivity fall between 0.0 and 1.0.of emissivity fall between 0.0 and 1.0.
8/6/2019 13 - Non-Contact Temp Measurement 2011
12/16
EmissivityEmissivity
When the emissivity of a body is known aWhen the emissivity of a body is known acompensation can be applied to thecompensation can be applied to the
pyrometer to receive a more accuratepyrometer to receive a more accurate
temperature readingtemperature reading
Emissivity is low for a good reflector, andEmissivity is low for a good reflector, andhigh for a poor reflector.high for a poor reflector.
Polished silver has an emissivity of .02Polished silver has an emissivity of .02
Dark asphalt has an emissivity of .95Dark asphalt has an emissivity of .95
8/6/2019 13 - Non-Contact Temp Measurement 2011
13/16
Blackbody CalibratorBlackbody Calibrator
Used to calibrateUsed to calibrateIR ThermocouplesIR Thermocouplesand handand hand--held IRheld IRpyrometers.pyrometers.
The target surfaceThe target surfacehas an emissivityhas an emissivityof near 1.0of near 1.0
Heated to aHeated to aspecific indicatedspecific indicated
temperature.temperature.
Use twoUse twotemperature pointstemperature pointsto calibrate and IRto calibrate and IR
pyrometer.pyrometer.
8/6/2019 13 - Non-Contact Temp Measurement 2011
14/16
Infrared Thermocouple or IRt/cInfrared Thermocouple or IRt/c The IRt/c sensorsThe IRt/c sensors areare
unpowered, low cost, andunpowered, low cost, andcancan measure surfacemeasure surfacetemperatures oftemperatures of materialsmaterialswithout touching.without touching.
They canThey can be directlybe directlyinstalledinstalled instead ofinstead ofcconventionalonventionalthermocouplethermocoupless..
All IRt/cs have aAll IRt/cs have aspecialized Optical &specialized Optical &Thermopile system whichThermopile system which
receives thereceives the heat energyheat energyradiated from objects theradiated from objects thesensor is aimed at, andsensor is aimed at, andconverts theconverts the heatheat ininto anto anelectrical millivolt signal.electrical millivolt signal.
8/6/2019 13 - Non-Contact Temp Measurement 2011
15/16
Infrared Thermocouple LinearityInfrared Thermocouple Linearity
IRt/c act like their standard thermocouple counterparts but have aIRt/c act like their standard thermocouple counterparts but have areasonable linearity over a very limited temperature range.reasonable linearity over a very limited temperature range.
They are therefore specified by their T/C type but in addition by theThey are therefore specified by their T/C type but in addition by the
desired temperature range..desired temperature range..
8/6/2019 13 - Non-Contact Temp Measurement 2011
16/16
Omega IR t/c Selection Example:Omega IR t/c Selection Example: