3200 Series
User Manual
Part No HA028651 Issue 11.0 July-12 71
11.5.1
Effect of Control Action, Hysteresis and Deadband
For temperature control ‘CONTROL ACTION’ will be set to ‘
rev
’. For a PID controller this means that the heater power
decreases as the PV increases. For an on/off controller output 1 (usually heat) will be on (100%) when PV is below the
setpoint and output 2 (usually cool) will be on when PV is above the setpoint
Hysteresis
applies to on/off control only. It defines the difference in temperature between the output switching off and
switching back on again. The examples below shows the effect in a heat/cool controller.
Deadband
can operate on both on/off control or PID control where it has the effect of widening the period when no
heating or cooling is applied. However, in PID control its effect is modified by both the integral and derivative terms.
Deadband might be used in PID control, for example, where actuators take time to complete their cycle thus ensuring
that heating and cooling are not being applied at the same time. Deadband is likely to be used, therefore, in on/off
control only. The second example below adds a deadband of 20 to the above example.
In an on/off controller, if CONTROL ACTION = rev then OP2 will be on when PV is below SP. OP1 will be on when the PV
is above SP. The outputs are, therefore, reversed in the above example.
Deadband OFF
Deadband ON
SP 300
o
C
HYST.C
HYST.H
OP1 On
Heating 100%
No OP
OP2 On
Cooling 100%
Heating and Cooling Type both
on/off
Setpoint = 300
o
C
Control Action = reverse
Heating Hysteresis = 8
o
C
Cooling Hysteresis = 10
o
C
Deadband = OFF
Heating off
at SP
(300
o
C)
Cooling on at
SP + HYST.C
(310
o
C)
Cooling off
at SP
(300
o
C)
Heating on at
SP – HYST.H
(292
o
C)
SP 300
o
C
HYST.C
HYST.H
Heating and Cooling Type
both on/off
Setpoint = 300
o
C
Control Action = reverse
Heating Hysteresis = 8
o
C
Cooling Hysteresis = 10
o
C
Deadband 50% of cooling hysteresis =
5
o
C
Heating
off at SP
(300
o
C)
Cooling on at
SP + HYST.C
(310
o
C)
Cooling off
at D.BAND
(305
o
C)
Heating on at
SP – HYST.H
(292
o
C)
D.BAND
OP1 On
Heating 100%
No OP
OP2 On
Cooling 100%
Power deadband
Summary of Contents for XST-2-0-12-1V1-E28
Page 16: ...12 FURNACE TROUBLE SHOOTING ...
Page 27: ...ɸ ...
Page 28: ...ɸ ...
Page 29: ......
Page 30: ......
Page 31: ...3216 3208 3204 User Manual 3200 Range Process Controller HA028651 11 Aug 2012 ...
Page 170: ...User Manual 3200 Series 138 Part No HA028651 Issue 11 0 July 12 21 Certificate of Conformity ...
Page 171: ......
Page 173: ...Model 2416 Process Controller User Manual Part No HA025041_12 Date August 2014 ...
Page 174: ...This page is intentionally blank ...
Page 259: ...This page is intentionally blank ...