Yokogawa Data Acquisition with PID Control CX2000 - Manual (Page 44)

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IM 04L31A01-01E
1.7 PID Parameter Settings
PID Number
PID parameter group number. The PID number can be set for each loop. When the PID
group number setting is “8”, you can select the PID number from 1 through 8. However,
if the PID group number is set to a smaller number, the maximum selectable PID number
is decreased accordingly.
Note
• The parameters that are registered to a single PID number include the PID constant,
output lower/upper limit, control action method, preset output value, shutdown function
ON/OFF, and manual reset value.
• In the zone PID method, a single PID number is assigned to each zone (zone specified by
reference points 5 and 6 is assigned a PID number of 6, for example). When the zone
changes, the parameter switches to the control parameters assigned to the PID number,
and the output is controlled accordingly.
PID Number Assignment
The PID number assignment operation varies depending on the PID selection method.
• When using the target setpoint selection method
The SP number and PID number are synchronized. By switching the SP number, the control
parameters (“PID parameters” in the settings) such as the SP and the PID constant are
changed to the control parameters registered to the corresponding PID number.
• When using the zone PID method
PID numbers are assigned to each zone beforehand. When the PV changes and
becomes a value of a different zone, the output is controlled automatically using the
PID parameters of the PID number that is assigned to that zone. The following
settings are required when using this method.
Reference Points
As shown in the following figure, reference points 1 to 6 (up to 7 zones) are specified to divide the
measurement span into zones. The number of reference points that can be specified is “PID
group number – 2.” As shown in the following figure, if the PID group number is 7, the number of
reference points is 5. If the number of reference points is 5, there are 6 zones.
No.1 PID
Maximum value of
measurement span
Reference point 1
Reference point 2
Reference point 3
Reference point 4
Reference point 5
Reference point 6
No.2 PID
No.3 PID
No.4 PID
No.5 PID
No.6 PID
No.7 PID
Minimum value of
measurement span
Change in the
PV.
If the current PV is here, PID
constant of PID No. 5 is used
for control.
Switching Hysteresis
You can set the hysteresis used in the zone switching in EUS (0.0% to 10.0%) of the
measurement span. The hysteresis is initially set to 0.5% of the measurement span.
No.1PID No.2PID No.1PID No.2PID
Reference
point 1
PV
Hysteresis width