Schedule of discussion topics
1. Advantages of non-contact temperature measurement
2. Physical principles of non-contact temperature
measurement
3. Definition and influence of emissivity
4. Fundamentals of optics
5. Applications and solutions
6. References
7. Criteria for selecting a pyrometer
8. Gobal features of KELLER pyrometer
9. Introduction of the series CellaTemp PQ/PL and PA
Chapter 1
Advantages
of non-contact temperature
measurement
Advantages
of non-contact temperature measurement
▪
▪
▪
▪
▪
▪
The technique employs non-wearing equipment.
Quick (takes only milliseconds).
Measurement of moving targets is possible.
Enables measurement of hazardous or inaccessible
objects.
Measurements as high as 3500°C are possible.
Nondamaging technique; especially suitable for poor heat
conductors, very small objects, sensitive surfaces or
hygienic products.
Chapter 2
Principles of non-contact
temperature measurement
A pyrometer is used for
temperature measurement
but it doesn´t measure the
temperature
Physics
of non-contact temperature measurement
 All matter that has a temperature (T) greater than
absolute zero emits electromagnetic radiation
(photon particles) due to the internal mechanical
movement of molecules.
 These photons travel at the speed of light and act
according to well-known optical principles.
They can be deflected, focused with a lens, or
reflected from reflective surfaces.
 Radiation thermometers or pyrometers are
measurement instruments which determine the
temperature of an object based on the infrared
radiation emitted from that object.
Thermal radiation
radio
infrared
visible
ultraviolet
The spectrum of radiation
useful for pyrometric measurement
ranges from 0.65 µm to 20 µm
wavelength
We refer to this range as
infrared radiation because it lies
within the red area of visible light
Planck´s Radiation Law
1,0E+04
Spectral radiance [W / cm³ µm]
1,0E+03
1,0E+02
5500K
(5326°C)
Max Planck, 1858 - 1947
3000K
(2726°C)
1,0E+01
1,0E+00
1500K
(1226°C)
1,0E-01
800K
(526°C)
1,0E-02
1,0E-03
500K
(226°C)
1,0E-04
200K
(- 73°C)
1,0E-05
0,1
1
10
Wavelength[µm]
100
Atmospheric transmission in the infrared spectrum
100
Transmission [%]
90
80
70
60
50
40
1m
30
20
10m
10
0
0
1
2
3
4
5
6
7
8
Wavelength [µm]
9
10
11
12
13
14
Temperature to wavelength relationship
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▪
Depending on the specific sensor, filter, and design of the pyrometer,
only the radiated energy within a narrow wavelength band will be
detected and converted into a quantity proportional to temperature.
The choice of the wavelength for a pyrometer depends primarily on
the temperature range to be measured.
Temperature range
Wavelength
-30 ... 1000 °C
100 ... 800 °C
180 ... 2500 °C
500 ... 3000 °C
600 … 3000 °C
8 ... 14 µm
1,8 ... 2,2 µm
1,1 ... 1,7 µm
0,8 ... 1,1 µm
0,85 … 0,91 µm
Measurement errors due to transmittance reduction
▪
▪
Under actual conditions, a
pyrometer´s sensor will not
always receive the entire amount
of thermal radiation emitted from
the target object.
Obstructions such as steam, dust,
sight glasses or equipment within
the instrument´s optical path will
reduce the radiation reaching the
pyrometer.
Messobjekt
Ideale Bedingungen
Sichtkegel
Pyrometer
Dampf,
Staub
Reale Bedingungen
Emittierte
Strahlung
Pyrometer
Partikel, Gase
Sichtfenster
Festes Hindernis
One-Colour Pyrometer
radiatoin
M(λ1) * ε1  T
l1
•0,1
•1
wavelength [µm]
•10
•100
Two-Colour Pyrometer
radiation
M(λ1) * ε1
 T
M(λ2) * ε2
l1
•0,1
l2
•1
wavelength [µm]
•10
•100
Block diagram CellaTemp PZ
as two-colour pyrometer
11
7
l1
8
9
10
A
A
A
MP
D
l2
D
12
1
2
3
4
5
6
1 measured object
5 ocular
9 A/D converter
2 lens, colour corrected
6 polarisation filter, adjustable
10 microprocessor
3 semitransparent mirror
7 detector
11 D/A converter
4 target marking
8 preamplifier
12 serial interface
The behaviour of a one-colour and two-colour
pyrometer due to reduction the infrared radiation
two colour channel
Quartz window t = 94 %
channel l1
channel l2
sieve t = 20 %
Contamination of a quartz glass window
Contamination detection
target object steam/dust
obstruction to
sighting path
sighting tube/
kiln wall
debris
protective
window
soiling
Pyrometer
CellaTemp PZ with integrated
contamination detection function
alarm signal
Chapter 3
Definition and influence
of emissivity
Definition of emissivity
„black body“
„real radiator“
=0
=0
=1
++=1
Emitted radiation = Absorbed radiation
Emitted radiation of a real body (R)
Emissivity (ε) =
Emitted radiation of a black body (S)
Components of radiation as detected by a pyrometer
Target
object
Transmitted
background
radiation
 * Obj.
Pyrometer
 * Back
 * Amb.
Reflected ambient
radiation
The radiation consists of the following components:
=( * Obj.) + ( * Amb.) + ( * ΦBack)

Emissivity of the target object

Reflection of the target object

Transmission of the target object
Emissivity based on material and wavelength
Emissivity depending on temperature
Measurement errors
At 1% change in emissivity or pollution,
depending on temperature and wavelength
16
4.5-4.9µm
8-14µm
14
Messfehler [°C]
12
1.9-2.5µm
10
8
1.1-1.7µm
6
0.78-1.06µm
4
0.63-0.67µm
2
0
0
500
1000
1500
Temperatur [°C]
2000
2500
3000
Chapter 4
The Fundamentals of Optics
Target spot diameter
in reference to the radiant energy received
d(95%)
d(90%)
The spot diameter is expressed as a
percentage of the radiant energy emitted.
d (95%)  3 x d (90%)
Distance ratio
d
a
Definition: distance ratio (D) =
distance (a)
target spot diameter (d)
With focusable optics, the maximum permissible measuring distance is
the distance ratio multiplied by the target spot diameter.
Energy distribution
of an imaged point source
at best focus
defocused by 0.5 mm
Chromatic aberration of lenses
relative change in focal length [%]
1 single lens made of crown glass
4,00
3,00
2 achromat cemented for the visible range
3 achromat cemented for the infrared range
1
2,00
2
1,00
0,00
3
-1,00
-2,00
400
500
600
700
800
900
1000 1100 1200 1300 1400 1500 1600
wavelength [nm]
Size of Source Effect for well and bad focusing
well focusing
bad focusing
910
900
temperature [°C]
890
880
870
860
850
840
830
820
810
800
0
5
10
15
20
25
target diameter [mm]
30
35
40
Chapter 5
Applications and solutions
Application rolling mill stand
Detect and document rolling
temperature before and after
the rolling stand.
Solution
One-colour pyrometer
with a short wavelength and
narrow wavelenght band
Two-colour pyrometer
with a short response time
and focusable, precision
optics
Application blast furnace
Application continuous caster
Knowing the strand temperature is important
for optimizing cooling
rates and controlling process speed.
A pyrometer with fiber optics can
be employed for temperatures up
to 250 °C without cooling
Application strip galvanizing
Pyrometers measure temperatures of
metal strips and sheets before they pass
through the molten zinc bath and during
coiling.
Measurement target within the gap
Application: Continuous extrusion of aluminium
The temperature is controlled by
using the CellaTemp PA 29
pyrometer with a special
wavelength to eliminate reflection
ration
CellaCast - Measurement systems for
non-contact and nonwearing temperature measurement

of continuous liquid iron streams

of discontinuous pour streams
2-3 Customer typology
Examples of pyrometer customers / applications (1)
Rolling mill
Centrifugal casting
Heat treatment
Billet heater
Asphalt
mixing plant
Cement production
2-3 Customer typology
Examples of pyrometer customers / applications (2)
Bulb production
Float glass production
Crystal growing furnaces
Bottle glass production
Soldering machines
Frozen foods
monitoring
Criteria for selecting a pyrometer
Global features of KELLER pyrometer
Introduction CellaTemp PQ / PL
Introduction CellaTemp PA
Thank you for your attention
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