INFRATHERM pyrometer ISR 50-LO
42
If the pyrometer is operating in ratio mode, the display shows “RA-
TIO” and the emissivity slope as well as the current signal strength is
shown as bar graph (see also 9.6 Switch-of level, 9.7 Contamina-
tion limit, 7.2 Thermal alignment and in the description of the Soft-
ware InfraWin under 10.7 Measurement color bar.
9.1.2
Signal strength as bar graph
With the bar graph of the signal strength a signal weakening can be
shown. This can be caused by contamination of the optics or a view-
ing window or by dust in the filed of view or a too small measuring
object. Normally this bar graph is used for surveillance of the level of
contamination of optics or window. It shows the measured intensity
compared to the intensity, a black body radiation source would have at a determined ratio temperature of the
pyrometer. Precondition for this is the correct adjustment of the emissivity slope K (a wrong adjustment
results in relative signals above 100%, in this case K has to be adjusted correctly. A bar graph with an addi-
tional value in numeric % value is shown in the window 10.7 measurement color bar in the software In-
fraWin.
9.1.3
Emissivity
ε
(Emi)
Note:
A setting of the emissivity (
ε)
is only possible in mono mode.
For a correct measurement in mono mode it is necessary to adjust the emissivity. This
emissivity is the relationship between the emission of an real object and the emission of
a black body radiation source (this is an object which absorbs all incoming rays and has
an emissivity of 100%) at the same temperature. Different materials have different
emissivities ranging between 0% and 100% (settings at the pyrometer between 5 and
100%). Additionally the emissivity is depending on the surface condition of the material, the spectral range of
the pyrometer and the measuring temperature. The emissivity setting of the pyrometer has to be adjusted
accordingly. Typical emissivity values of various common materials for the two spectral ranges of the instru-
ments are listed below. The tolerance of the emissivity values for each material is mainly dependent on the
surface conditions. Rough surfaces have higher emissivities.
If the operating mode „MONO“ is selected, additionally to the current
temperature the display shows the emissivity. Then the emissivity
can directly be changed via the and keys, the effect to the
measuring temperature can be observed immediately. Upon comple-
tion the settings, the value must be taken over with “Enter”.
If the pyrometer is operating in mono mode, the display shows
“MONO” and the current emissivity is shown.
9.1.4
Table for emissivity / emissivity slope
Emissivity values and emissivity slope values of various common materials are listed below:
Measuring object
ε
(at 0.9 µm)
K
Measuring object
ε
(at 0.9 µm)
K
„Black body furnace“
1
1
Nickel
0.22
Steel heavily scaled
0.93
1
Gold, Silver, bright
0.02
Steel rolling skin
0.88
1.00 ... 1.01
Porcelain glazed
0.6
1
Steel, molten
0.3
Porcelain rough
0.8 ... 0.9
1
Slag
0.85
1
Graphite
0.8 ... 0.92
1.01
Chromium, bright
0.28 ... 0.32
Chamotte
0.45 ... 0.6
1
Brass oxidized
0.65 ... 0.75
Earthenware, glazed
0.86 ... 0.9
1
Copper, oxidized
0.88
Brick
0.85 ... 0.9
1
Zinc
0.58
Soot
0.95
0.95
Settings:
5 %
.
.
.
100%
Operation mode
Emissivity
slope
Display of the
signal strength
Emissivity
operating
mode
Emissivity
