INFRATHERM
pyrometers IS 5 · IS 5-LO · IGA 5 · IGA 5-LO
51
10.8.2 Self
tuning
algorithm
In approaching the desired temperature, the control parameters Xp, Ti and Td can be determined using the
controller. Normally, the determined parameters can achieve the desired temperature without significant
over- or undershooting. The self-tuning algorithm is only carried out by the device if there is a deviation from
the desired temperature of min. 5% (of the (adjusted) temperature range). The biggest possible output is
emitted (i.e. 0%, if actual value > desired value). The output is reversed when the midway point to the de-
sired temperature is reached. The resulting oscillation is used to determine the controller parameters. The
determined parameters are transferred to the controller and used to continue approaching the desired tem-
perature.
If the difference between the actual value and the desired value is > 15% of the measuring range, it may be
necessary to carry out the self-tuning process in stages, as otherwise the parameters determined after the
'midway point' do not correspond sufficiently to the conditions of the desired temperature. For this purpose,
first a desired temperature which is approx. 10% of the final desired temperature is aimed at, and then, in the
second stage, the self-tuning algorithm is started to reach the final desired temperature.
Problems are generally posed by directly controlled systems where there are high contrasts between the
cooling time constant and the heating up time constant. For example, in many cases a metal block with a
high thermal capacity is heated with electric heating cartridges. The heat dissipates from the block only
through radiation. In this case, even the self-tuning algorithm will give unsatisfactory results; then it is neces-
sary to reduce the output delimitation to avoid an overshooting of the temperature.
10.9
Measurement (color bar)
This window displays:
•
current temperature, graphically as color bar and
numerically
•
Temperature range or adjusted sub range
•
file size and quantity of the measured values of the
current measurement emissivity
ε
•
the internal temperature of the pyrometer (T
int
)
•
minimum (T
min
) and maximum temperature values
(T
max
) of the measurement
The color bar display shows the span of the temperature range
or the adjusted sub-range. Entering temperature values in the
white fields on the left and right side of the color bar, limits for
the color change of the color bar can be set. These limits can
also be changed by moving the small bar with the PC mouse.
The color bar displays temperatures within the two limits in
green color, outside the limits in red color.
Additionally in this window the emissivity can be entered. If the
emissivity is changed, a corresponding temperature change is
directly viewable.
The targeting light ( ) can be switched on or off, if the pyrome-
ter is equipped with it.
