Unipulse F805AT-BC, Operation Manual

Page: 98 / 202

6.SETTING AND ADJUSTMENT OF READING
83
Proportion (P)
Wide proportional band (P) makes the
variation of control rate relatively small
(smaller slope in the figure to the right),
rendering the time required to attain
equilibrium longer. On the other hand,
overshoot and hunting becomes less
obvious.
Narrow proportional band provides
opposite characteristics: larger
overshoot and hunting, and shorter time
to reach equilibrium.
In proportional action, feed rate often
attain equilibrium while maintaining
residual small deviation from target
value, which is called “offset”.
Narrower proportional band (P) is
effective to reduce the offset.
Wider proportional band is used to
obtain more stable feed rate, with
correspondingly large offset.
* Empirically, proportional bandwidth
between 50.00 – 200.00 % FS is
recommended.
Operation
Control rate [%]
Flow
0
Target
Smaller proportional band
Larger proportional band
[Proportional action]
[t/g],[kg/h]
Actual
Initial
100
control
rate
flow
Flow
Time
0
Target
Offset
Small proportional band
Large proportional band
Correct proportional
[Proportional action]
band
(with hunting)
(large offset)
Optimal proportional band
Proportional band
Optimal proportional band
Proportional band
Large proportional band
Small proportional band
too wide
(with large offset)
too narrow
(require longer equilibrium time)
MODE EACH CODE
→
PROPORTION (P)
→
Range: 0.01 – 999.99% (5 digits, decimal place fixed to 2
nd
position)