Despatch P1400+ Temperature Controller User Manual
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below. If the process variable deviates from the setpoint by a margin greater than this value, alarm
1 becomes active.
Display code =
dAL1
, Default value = 5.
Also refer to
Alarm Operation
and
Deviation Alarm 2 Value
.
Deviation Alarm 2 Value
Type: General Parameter
Applicable only if Alarm 2 is selected as a Deviation Alarm. It is similar to Deviation Alarm 1 Value.
Display code =
dAL2
. Default value = 5.
Also refer to
Alarm Operation
and
Deviation Alarm 1 Value
.
Differential (On-Off Hysteresis)
Type: Controller Parameter
A switching differential used when one or both control outputs have been set to On-Off. This
parameter is adjustable within the range 0.1% to 10.0% of input span; the default value is 0.5%. The
differential band is centred about the setpoint.
Relay chatter can be eliminated by proper adjustment of this parameter. Too large a value for this
parameter will increase amplitude of oscillation in this process variable.
Display code =
diFp
for primary only differential,
diFS
for secondary only differential &
diFF
for
primary and secondary differential.
Also refer to
Input Span
and
On-Off Control
.
Direct/Reverse Action of Control Outputs
Type: Controller Definition
Direct action is typically used with cooling applications; On-Off direct outputs will turn on when the
process variable exceeds setpoint. Proportional direct outputs will increase the percentage of output
as the process value increases within the proportional band. Reverse action is typically used with
heating applications; On-Off reverse outputs will turn off when the process variable exceeds
setpoint. Proportional reverse outputs will decrease the percentage of output as the process value
increases within the proportional band. The Secondary Output will be direct whenever the Primary
Output is selected as reverse. The Secondary Output will be reverse whenever the Primary Output
is selected as direct.
Also refer to
Control Type
,
On-Off Control
,
PID
,
Primary Proportional Band
and
Secondary
Proportional Band
Display Strategy
Type: General Parameter
Alters the parameters displayed in normal operator mode. For example a controller could display PV
+ SP, PV + adjustable SP, PV + Ramping SP, PV only or SP only. Display strategy 6 will allow read
only access to the setpoint values in Operator Mode, Setup Mode must then be entered to change
the setpoint.
Display code =
diSp
Also refer to
Process Variable
,
Setpoint
and
Setpoint Ramping
.
Input Filter Time Constant
Type: General Parameter
This parameter is used to filter out extraneous impulses on the process variable. The filtered PV is
used for all PV-dependent functions (display control, alarm etc). The time constant is adjustable from
0.0 seconds (off) to 100.0 seconds in 0.5 second increments.
Display code =
FiLt
, Default value = 2.0 seconds.
Also refer to
Process Variable
.
Input Range
Type: General Definition
This is the overall process variable input range and type as selected by the
InPt
parameter in
Configuration Mode.
Also refer to
Input Span
.