Process Sensors Sensor Therm METIS M311 Operating Manual page 27

METIS M311 / M322 / H311 / H322 (12-pin)
curves are identical (at the same emissivity setting), then the emissivity slope is 1. Do they run parallel, so the
correct value for the emissivity ratio must be found, such by comparative measurement with a thermocouple
and subsequent ratio setting until the temperatures match.
6.2.4 Switch-off Level / Signal Strength / Dirty Window Monitoring
2-color pyrometers measure even with reduced signal strength, such as those occur in a partially filled measur-
ing field, or dust, smoke, steam, or a window in the beam path between pyrometer and the measuring object. If
the signal strength is too low for a reliable measurement, the measurement is switched off to avoid measure-
ment errors. In this case, the beginning of the temperature range is set to the outputs, i.e. 0 or 4 mA depending
on the setting.
The switch-off limit can be set between 2 and 90%, recommended for a reliable measurement is a minimum
value of 10%.
Furthermore, a digital output can be set using the SensorTools software, which is activated when the signal
strength falls below a certain value. This e.g. can be used as contamination or dirty window monitoring.
|INFO|
The lower the signal strength, the more likely it can affect the measurement of ambient light and reflec-
tions.
6.2.4.1 Switch-off Verification
If the signal strength is so low that a switch-off occurs, a time can be entered that defines when this switching-
off actually takes effect.
6.2.5 Emissivity ε (when used in 1-color mode)
The pyrometer also can be used in 1-
color mode, the measurement corre-
sponds to that of a conventional radia-
tion pyrometer. In this measuring
mode the input of an emissivity is nec-
essary.
The emissivity indicates the radiation
capacity of an object to be measured
relative to a Blackbody Source with the
same temperature. To obtain correct
readings, the emissivity must be taken
into account in the measurement and
adapted for the respective measuring
material on the pyrometer. Each mate-
rial has a max. emissivity of 1.00 which
can be set, an adjustment of up to 1.20
can be used. The emissivity adjust-
ment above 1.00 allows for tempera-
ture corrections due to higher back-
ground reflection.
In principle applies: to measure metals
in a short-wavelength spectral range
as possible, as here the emissivity is
higher than in the long-wave range.
The specified values are guide values,
which were determined in the laborato-
ry and confirmed in application-
Measuring object
Blackbody Source
Aluminum, shiny
Aluminum, oxidized
Aluminum, sandblasted, rough
Aluminum, black anodized
Lead oxidized
Bronze
Iron, liquid
Iron, shiny
Iron, oxidized
Graphite
Gold, shiny
Inconel, shiny
Inconel, oxidized
Copper, shiny
Copper, oxidized
Magnesium, shiny
Magnesium, oxidized
Brass, shiny
Brass, oxidized
Molybdenum, oxidized
Nickel
Emissivity
Ɛ (Epsilon)
M311/H311 M322/H322
0.7-1.1 µm 1.45-1.8 µm
1 1
n.s. 0.05-0.2
n.s. 0.3-0.4
n.s. 0.4-0.5
n.s. 0.9
n.s. n.s.
0.2-0.4 0.2-0.4
0.15-0.3 0.1-0.25
0.3-0.4 n.s.
0.7-0.9 0.65-0.85
0.8-0.92 0.8-0.9
0.02-0.05 0.02-0.05
0.35-0.45 0.4
0.65-0.75 0.6-0.7
0.10 0.05-0.1
0.3-0.7 0.2-0.8
n.s. 0.15-0.2
n.s. 0.3-0.5
0.5-0.7 0.5-0.7
0.6-0.8 0.6-0.7
0.7-0.9 0.7-0.85
0.22 0.15-0.2
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