IDEC MicroSmart Pentra - Manual (Page 101)

C ONFIGURING PID M ODULE USING W IND LDR
6-36 FC5A MicroSmart PID Module User’s Manual FC9Y-B1283
(3) Control Register+54: Heating/Cooling Control
The heating/cooling control can be enabled. When it is difficult to control a target process with heating control
only, cooling control can be added to perform the heating/cooling control.
Example: Heating/Cooling control uses both heating and cooling outputs and is suitable for the heat
producing processes such as extruders or for temperature control at near the ambient temperature,
such as environment testers.
(4) Control Register+20: Set point (SP)
Any value within the following valid range can be configured as the set point (SP).
The valid range of set point (SP) when the input type is thermocouple or resistance thermometer:
Set point (SP) lower limit
≤ Set point (SP) ≤ Set point (SP) upper limit
The valid range of set point (SP) when the input type is voltage or current:
Linear conversion minimum value
≤ Set point (SP) ≤ Linear conversion maximum value
If the input type or input unit type is changed, confirm the valid range of set point (SP) and configure an
appropriate value.
(5) Control Register+94: Proportional Term
Either proportional band or proportional gain can be selected to use. The proportional band, which is
expressed in percentage form (%), is the span of the input necessary for the output manipulated variable (MV)
to change from 0% to 100%. The proportional gain is the coefficient to calculate the output manipulated
variable (MV) of the proportional action. The proportional gain can be obtained as the quotient of 100 and the
proportional band.
Example: When the proportional band is 50%, the corresponding proportional gain will be 2% (100/50).
(6) Control Register+26: Proportional Band/Proportional Gain
The output of the proportional action varies in proportion to the deviation between the set point (SP) and the
process variable (PV). When the heating/cooling control is enabled, this parameter becomes the heating
proportional band. The control action will be ON/OFF control when the proportional band/proportional gain is 0.
If the proportional band is broadened (proportional gain is made smaller), the control output starts turning on or
off at the significantly low temperatures from the set point (SP), overshoot or hunting is reduced; however, it
takes time for the process variable (PV) to reach the set point (SP), and the offset between the process
variable (PV) and the set point (SP) is broadened.
If the proportional band is narrowed (proportional gain is made larger), the control output starts turning on or off
at around the set point (SP), the time until the process variable (PV) reaches the set point (SP) is shortened,
and the offset is small; however, the hunting phenomenon is frequent. If the proportional band is greatly
narrowed, the control action becomes similar to the ON/OFF control action.
An appropriate proportional band/proportional gain for the control target can be automatically calculated using
auto-tuning (AT) function. It is unnecessary to configure the proportional band/proportional gain in the
WindLDR when using the auto-tuning (AT) function.
(7) Control Register+27: Integral Time
In the proportional control action, the offset is generated even when the control is stabilized. The integral action
corrects the offset. The integral action is disabled when the integral time is 0.
The integral time is a coefficient to determine the output manipulated variable (MV) of the integral action.
If the integral time is shortened too much, the integral action becomes strong. The offset can be corrected in a
shorter time; however, the hunting phenomenon may be caused over a long cycle. On the contrary, if the
integral time is extended too much, the integral action becomes weak and it takes time to correct the offset.
An appropriate integral time for the control target can be automatically calculated using auto-tuning (AT)
function. It is unnecessary to configure the integral time in the WindLDR when using the auto-tuning (AT)
function.
Cooling
Control
Target
PID
Module
Heating