WIKA CS4L - Manual (Page 37)

Operating Instructions Temperature Indicating Controller CS4H / CS4L
V1.1 • 05/2006 - 37 -
For A2 output, terminals 12 and 13 are used.
A1 and A2 indicators light up when between the output terminals is ON, and goes out when between them
is OFF.
7.6 SV1/SV2 external selection action
If the serial communication is applied, this function is disabled.
8. Control action explanations
8.1 PID
(1) Proportional band (P)
Proportional action is the action which the control output varies in proportion to the deviation between
the setting value and the processing temperature.
If the proportional band is narrowed, even if the output changes by a slight variation of the processing
temperature, better control results can be obtained as the offset decreases.
However, if the proportional band is narrowed too much, even slight disturbances may cause variation
in the processing temperature, control action changes to ON/OFF action and the so called hunting
phenomenon occurs.
Therefore, when the processing temperature comes to the balanced position near the setting value and
a constant temperature is maintained, the most suitable value is selected by gradually narrowing the
proportional band while observing the control results.
(2) Integral time (I)
Integral action is used to eliminate offset. When the integral time is shortened, the returning speed to the
setting point is accelerated. However, the cycle of oscillation is also accelerated and the control be-
comes unstable.
(3) Derivative time (D)
Derivative action is used to restore the change in the processing temperature according to the rate of
change. It reduces the amplitude of overshoot and undershoot width.
If the derivative time is shortened, restoring value becomes small, and if the derivative time is made
longer, an excessive returning phenomenon may occur and the control system may be oscillated.
SV1
SV1/SV2
external
selection
14
17
14
17
SV2 SV1 SV2
SV1 SV2
Lit Unlit Unlit Lit
Indication
Green
OFF
ON
High/Low limits alarm with standby
SV setting
A1
set point
A1
set point
Alarm action
Alarm output
A1 hysteresis
: A1 output terminals between 7 and 8 is ON.
: Standby functions.
: A1 output terminals between 7 and 8 is ON or OFF.
: A1 output terminals between 7 and 8 is OFF.