West Control Solutions 8700+ - Manual (Page 152)

1 /
4
-DIN, 1 /
8
-DIN & 1 /
16
- DIN Controllers & Indicators - Product Manual
59305, Issue 7
– March 2014 Glossary Page 147
Figure 43. Overlap/Deadband
PI Control Type: Controller Definition
Proportional and Integral (PI) Control is used to control Modulating Valves. It is similar to PID
Control, but without Derivative (Rate) action that causes excessive valve movement.
Also refer to Modulating Valve, PID Control, Rate, Tuning and Valve Motor Drive Control.
PID Control Type: Controller Definition
Proportional Integral and Derivative control maintains accurate and stable levels in a process
(e.g. temperature control). It avoids the oscillation characteristic of On-Off control by
continuously adjusting the output to keep the process variable stable at the desired setpoint.
Also refer to Control Action, Control Type, Automatic Reset, Controller, Manual Mode, On-Off
Control, PI Control, Primary Proportional Band, Process Variable, Rate, Secondary
Proportional Band, Setpoint, Tuning and Valve Motor Drive Control.
Overlap/Dead
band
Output 1
Output 1
Output 2
Output 2
Output 2
Process Variable
Process Variable
Process Variable
Proportional Band 1
Proportional
Band 1
Proportional
Band 1
Proportional Band 2
Proportional
Band 2
Proportional Band 2 = 0
Output 1
Output 1
Output 1
Output 1
Output 2
Output 2
Output 2
Overlap
(positive value)
Deadband
(negative value)
Negative values Positive values
OVERLAP
WITH PID
DEADBAND
WITH PID
OVERLAP &
DEADBAND
WITH ON/OFF
Out
put
P
owe
r
(%
)
Out
put
P
owe
r
(%
)
Out
put
P
owe
r
(%
)
Out
put 2
ON
Out
put 2
OFF
ON/OFF Differential
Overlap/Dead
band
Output 1
Output 1
Output 2
Output 2
Output 2
Process Variable
Process Variable
Process Variable
Proportional Band 1
Proportional
Band 1
Proportional
Band 1
Proportional Band 2
Proportional
Band 2
Proportional Band 2 = 0
Output 1
Output 1
Output 1
Output 1
Output 2
Output 2
Output 2
Overlap
(positive value)
Deadband
(negative value)
Negative values Positive values
OVERLAP
WITH PID
DEADBAND
WITH PID
OVERLAP &
DEADBAND
WITH ON/OFF
Out
put
P
owe
r
(%
)
Out
put
P
owe
r
(%
)
Out
put
P
owe
r
(%
)
Out
put 2
ON
Out
put 2
OFF
ON/OFF Differential