YOKOGAWA F3CU04-0S, User Manual

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C6-4
IM 34M06H62-02E 2nd Edition : June 2008-00
C6.3 Integral Time and Manual Reset Value

About Integral Time
A function that automatically reduces the offset (steady state deviation) that would
theoretically be unavoidable in a proportional operation is called an integral action (I
action), with the integral time (TI) parameter defining the sensitivity of the integral action.
The integral action increases or decreases its output continuously in proportion to the
integral of the deviation (the product of deviation and its duration).
The integral action is used in conjunction with the normal proportional action to yield the
proportional integral action (PI action).
Integral Time (TI) is defined as the length of time required for an integral action alone to
produce the same amount of change that a proportional action alone would produce,
given a stepped deviation. The longer the integral time, the slower will be the output
change. Conversely, the shorter the integral time, the faster will be the output changes.
Integral Time (n.TI) (n = 1-4)
e : Deviation
P : Proportional band
T
I
: Integral time
Output =
e +
100
P
1
T
I
P=100%
Deviation
Output data (%)
(ON time ratio)
Shorter
integral time
Longer integral
time
Output change due to
I action
Output change due to
P action
Integral time
Time

edt
Figure C6.5 Integral Time
- To turn off the integral action, set the Integral Time (TI) parameter to “0: OFF”.
- To eliminate the offset when TI=OFF, use the Manual Reset (MR) parameter.

Manual Reset Value
The Manual Reset (MR) function is used to manually reduce the offset (steady-state
deviation) in proportional action (P control) or proportional derivative action (PD control)
where Integral Time (TI) is set to OFF. The function allows you to shift the control output
by a certain value so as to reduce the offset.