18
• Menu (Details):
TEMPERING:
1. Control:
1) Control Mode:
Internal (int):
The temperature is regulated according to
the internal temperature sensor.
Extern (ext):
The temperature is regulated according to
the external temperature sensor.
2) Control parameters:
Automatic:
The optimal control parameters for PID tem-
perature control are determined automatically. This is
the recommended mode.
Selecting "Automatic" allows you to set the dynamics
for temperature control.
Ts
must be adjusted to match the response character-
istic (total of all time constants) of the closed loop con-
trolled system, so that the control variable can deliver a
uniform and measurable change in the control devia-
tion.
Ts
values that are too small or too large can lead
to instability of the controller.
Prop_Bp:
Proportional Band Maximum.
Prop_Bn:
Proportional Band Minimum.
The Proportional Band is the range below (Prop_Bp) and
above (Prop_Bn) the set value in which the control out-
put value is calculated via the difference between the
actual and the set value and the PID parameters.
Examples of non-optimal settings:
3) Fluids:
Under the option "Fluids", a variety of fluids can be selected.
The selected fluid limits the setting range of the target
temperature. See table in the section “Fluids (Standard
information for
IKA
fluid)“.
The maximum and minimum temperature values of the
selected fluid can be set within these limitations.
2. Limits:
Under the option "External (ext)", the maximum and
minimum temperature for external temperature control
can be set.
Under "l Δ T (int - ext) l", the maximum difference be-
tween the internal and external temperature can be set.
The function limits the absolute temperature difference
between the external system and internal bath during
the heating up and cooling down process. This can pro-
tects sensitive device like the glass reactors from thermal
shock (e.g. glass break).
Kp too high
°C
t
Ti too high
°C
t
Kp too low
Ti too low
°C
t
Td too high
°C
t
Fig. 26
Manual:
The control parameters for PID temperature
control can be set manually.
"Manual" should only be used in the event of special
temperature control requirements.
When "Manual" is selected, the following parameters
can be set for "Internal (int)" and "External (ext)" tem-
perature control:
Kp:
Proportional coefficient
The proportional coefficient
Kp
is the controller ampli-
fication and determines how strongly the control devia-
tion (the difference between the target temperature and
actual temperature) directly affects the control variable
(on-time of the cooling).
Kp
-values that are too large
can lead to the controller overshooting.
Ti:
Integral time
The integral time
Ti
(s) is the correction time and de-
termines how strongly the duration of the control de-
viation affects the control variable.
Ti
compensates for
an existing control deviation. A high
Ti
means a smaller
and slower effect on the control variable.
Ti
-values that
are too small can lead to instability of the controller.
Td:
Differential time
The differential time
Td
(s) is the derivative time and de-
termines how strongly the rate of change of the control
deviation affects the control variable.
Td
compensates
for rapid control deviations. A high
Td
means a smaller
and slower effect on the control variable.
Td
-values that
are too large can lead to instability of the controller.
Ts:
Sampling time
The sampling time
Ts
(s) is the time interval over which
the control deviation is determined and the respective
control variable (dependent on
Kp
,
Ti
and
Td
) is cal-
culated.
Fig. 25
(cooling curve in “Automatic” mode)
°C
t
