LumaSense Technologies ISQ 5-LO - Handbuch (Seite 22)

IMPAC pyrometers ISQ 5 · ISQ 5-LO
22
 Integral time Ti:
As the temperature deviates from the “desired temperature”, a corresponding signal which changes over
the time is transmitted to the analog output until the deviation reaches zero.
 The integral time can be set in two different formats: “min:s” for the range of 0.00 s to 99.99 s;
”s” for the range of 0:01 min to 99:99 min. In the first case, an update of the integral error will occur every
10 ms, in the second case, every second.
With a set of T
i
= 0 no integral proportion will be calculated.
 Rate time Td:
The rate time enables the initial amplitude to be jump-started. The rate time can be set in two formats:
In the range from 0.00 s to 99.99 s or from 0:01 min to 99:99 min. The rate time will be recalculated in
the interval of the entered time. With a set of T
d
= 0 no rate time proportion will be calculated.
 Output delimitation Ymax (0.1 ... 100%):
The output delimitation Y
s
can be limited to a maximum value of < 100%. A negative setting of the output
delimitation follows a reversal of the direction of action.
In case of a two-state controller this means for example:
Y
max
= +80%: (actual value > desired value)  output Y
s
= 0%
(actual value < desired value)  output Y
s
= 80%
Y
max
= -80%: (actual value > desired value)  output Y
s
= 80%
(actual value < desired value)  output Y
s
= 0%
 Apply:
Click the apply button to set the entered values (under “New”) into the pyrometer.
 Apply + Self Tune:
Click the Apply + Self Tune button to set the entered values (under “New”) into the pyrometer and simul-
taneously start the automatic self-tuning algorithm.
 Stop:
If the temperature is getting out of control, the whole process can be stopped by pressing the
stop button.
 Output Y:
If the output Y is set to “manu.”, the analog output signal can be controlled directly. In this case the bar
graph on the right side has the function as a sliding controller and the temperature adaptation can be ob-
served directly.
9.8.2
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.