IDEC MicroSmart Pentra - Manual (Page 37)

PID M ODULE M AIN F UNCTIONS
4-14 FC5A MicroSmart PID Module User’s Manual FC9Y-B1283
Heating/Cooling Control
When it is difficult to control the target process with heating control only, cooling control can be added to
perform the heating/cooling control. Control results derived from the set point (SP) and process variable (PV)
are outputted to 2 outputs, heating output (CH0) and cooling output (CH1). If the process variable (PV) is
higher than the set point (SP), cooling output will be turned on. If the process variable (PV) is lower than the
set point (SP), heating output will be turned on. The area in which both heating and cooling outputs are turned
on can be configured as overlap. The area in which neither heating output nor cooling output is output can be
configured as dead band.
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 ambient temperature such as
environment testers.
Difference Input Control
Difference input control is the control to keep the input difference between input CH0 and input CH1 at the
same level. When the difference input control is selected, input CH0 and input CH1 are independently
measured, and the difference between those inputs is used as process variable (PV). PID module controls
output so that the difference between those inputs is matched to the set point (SP).
Example 1: Controlling the liquid level difference of 2 tanks
The PID module measures the liquid levels of 2 tanks and controls output to keep liquid level difference
between Tank A and Tank constant.
Example 2: Cabinet Interior Dew Condensation Prevention
The PID module measures interior and external temperatures of the cabinet and controls output to keep the
temperature difference between interior and external cabinet constant so that dew condensation inside the
cabinet can be prevented.
Cooling
Control
Target
PID
Module
Heating
PID
Module
Cabinet
Input CH1
Input CH0
Output CH0
Fan
Interior
Temperature
External
Temperature
PID
Module
Tank A
Input CH1
Input CH0
Tank B