LumaSense Technologies ISR 12-LO/GS - Handbuch (Seite 16)

IMPAC pyrometers ISR 12-LO/GS
16
Pre-run time (0 ... 9.9 s):
A certain pre-run time can be set in addition to the start-up condition. This additional period delays the start
of the temperature calculation and can be necessary e.g. if sparks disturb the measurement at the begin-
ning.
Measuring time (0 ... 9.9 s, 0 = auto):
As a standard the measuring time is running in the auto mode, i.e. automatic recognition of start and end
process in combination with a continuous controlling of the start-up condition. If the start-up condition is not
longer fulfilled (temperature below beginning of sub range = end of pouring process), the system starts with
the calculation of the pouring stream temperature. For this calculation it removes the last 1024 temperature
values, makes an average of the remaining values and shows the calculated temperature on the display.
If a fixed measuring time is set, the system is recognizing the start process automatically and is using this
period for the calculation of the temperature and shows the calculated temp. on the display.
In both modes the temperature is displayed until the next calculated temperature is available.
Follow-up time (0 ... 9.9 s):
Very often at the end of pouring processes liquid iron drops after closing the valve or the operator opens the
valve for a short final refill manually. E.g. this can cause problems that the instrument starts a new pouring
stream measurement although it belongs to the running process. A certain follow-up time can avoid a early
restart of the measurement.
Conclusion:
This are all details which are necessary for a correct detection and measurement of a pouring stream. The
calculation of the average temperature occurs if the measuring condition is not fulfilled anymore or the ad-
justed time is expired. The last 1024 measurement values are not included in the temperature calculation to
avoid measurement errors (e.g. caused by sparks or iron drops).
Example graph:
Measuring condition: x % of 1024 measure-
ment values above beginning of sub range
Time [s]
M
eas
uri
ng t
em
perat
ure [
°C]
Measuring graph of the pyrometer
Pre-run time 0 ... 9.9 s
Measuring time („auto“ mode)
1024 values (fixed)
without consideration
Follow-up time 0 ... 9.9 s
Temperature sub range
of the pyrometer
Display of the calculated
pouring stream temp.
8.2
Emissivity
ε
/ emissivity slope K
Emissivity slope (K =
ε
1 /
ε
2) only in ratio mode.
Emissivity (
ε)
setting only in mono mode.
For a correct measurement 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 ab-
sorbs 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 10 and 100%). Ad-
ditionally the emissivity is depending on the surface condition of the material, the spectral range of the py-
rometer and the measuring temperature. The emissivity setting of the pyrometer has to be adjusted accord-
ingly. Typical emissivity values of various common materials for the two spectral ranges of the instruments
are listed below. The tolerance of the emissivity values for each material is mainly dependent on the surface
conditions. Rough surfaces have higher emissivities.