Yokogawa Data Acquisition with PID Control CX2000 User Manual

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1-33

IM 04L31A01-01E

Explanation of Functions

Reference Deviation
During control operation, the operation can be switched automatically to a preset PID
constant (PID constant with the largest PID number. For example, if the PID group
number is 8, the PID constant of PID number 8.) when the deviation between the SP and
the PV exceeds the “reference deviation” setting. For example, when the deviation is
large, you can increase the proportional gain (decrease the proportional band) to make
the output reach the SP quickly. The switching of the PID constant by the reference
deviation has precedence over the switching of the PID constant by the zone PID. When
the actual deviation becomes smaller than the “reference deviation” setting, the CX2000
returns to the operation using the PID constant assigned to the zone corresponding to
the PV at that point.
The previously described switching hysteresis is also applied to the reference deviation.

Maximum value
of measurement span

Minimum value
of measurement span

No.1 PID

No.2 PID

No.8 PID

Reference deviation value

Reference
point 2

Reference
point 1

Reference deviation value

If the PID group number is 8 and
the PV exceeds the reference
deviation value, the operation
switches to the PID constant of
PID number 8 regardless of the zone.

PID Constant

Proportional Band (P)
The proportional band is specified in the range of 0.1 to 999.9% of the measurement span.
Integral Time (I)
The integral time is set in the range of 0 to 6000 s.
Derivative Time (D)
The derivative time is set in the range of 0 to 6000 s.

Control Output Limiter

The control output limiter is a function that allows the upper and lower limits of the
operation range of the control output (output limiter) regardless of operation mode.
Selectable range of upper/lower limits: –5.0% to 105.0% (where upper limit > lower limit)

–5.0%

105.0%

Upper limit of output

Lower limit of output

Actual output fr

om the terminal

Original variable range

Selectable range: –5.0% ≤ lower limit of limiter < Upper limit of limiter ≤ 105.0%

Actual output
change range

Lower limit of limiter Upper limit of limiter

Variable range

1.7 PID Parameter Settings