Yokogawa Data Acquisition with PID Control CX2000 - Manual (Page 53)

1-41
IM 04L31A01-01E
Explanation of Functions
3
2
1
4
5
6
7
8
9
10
11
12
13
14
1.11 Program Control Related Settings
Selecting the PID Selection Method
When program control is turned ON, select segment PID method (zone PID selection
OFF) or zone PID method.
• Segment PID method
Segment PID method is a function in which the PID setpoint is switched for each
segment according to the program pattern setting during program operation.
Therefore, this method is suitable for control in which the PID constant is changed
during ramp-up and ramp-down in the same PV region.
Process
value
No.2PID
SEG1 SEG2 SEG3 SEG4 SEG5 SEG6 SEG7
No.1PID No.3PID
1000.0
500.0
0.0
If the current operation is
at the 5th segment, the
PID constant of No. 1 is
used.
• Zone PID method
Zone PID method is a function in which the PID setpoint is automatically switched
according to the PV. Therefore, the same PID constant is used in the same PV
region regardless of the ramp-up and ramp-down program operation. This method is
used on equipment such as reactors in which the chemical reaction gain varies
depending on the temperature.
As shown in the following figure, the measurement span can be divided into up to 7
zones using reference points 1 to 6. An optimum PID constant can be assigned to
each zone. Therefore, even if the PV changes and crosses between the zones, the
output is controlled automatically using the PID constant that is assigned to each zone.
No.1PID
Minimum value of PV span
Maximum value of PV span
Reference point 1
Reference point 2
Reference point 3
Reference point 4
Reference point 5
Reference point 6
No.2PID
No.3PID
No.4PID
No.5PID
No.6PID
No.7PID
Change in the process value (PV)
If the current process value (PV) here,
control using the PID constant of No. 6.