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Deviation Alarm 2 Value
Applicable only if Alarm 2 is selected as a Deviation Alarm. It is similar to Deviation Alarm 1
Value.
Display code = D5+3 . Default value = 5.
Also refer to Alarm Operation and Deviation Alarm 1 Value.
Differential (On-Off Hysteresis)
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 = D<&1 for primary only differential, D<&: for secondary only differential &
D<&& for primary and secondary differential.
Also refer to Input Span and On-Off Control.
Direct/Reverse Operation of Control Outputs
Direct operation 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
operation 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 On-Off Control, PID, Primary Proportional Band and Secondary Proportional
Band
Display Strategy
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 = D<:1
Also refer to Process Variable, Setpoint and Setpoint Ramping.
Elapsed Time
The total accumulated time that Alarm 1 has been active on an Indicator since this parameter
was last reset. This does not include the time when the alarm condition has cleared. The
Elapsed Time is not affected by the Alarm 2 and Alarm 3 status.
Also refer to Alarm Operation, Exceed Time and Indicator.
Exceed Condition
A state that occurs when the Process Variable exceeds the Limit Setpoint value. E.g. if the
PV is above the Limit SP when set for high limit action, or below the Limit SP for low limit
action. The Limit Controller will shut down the process when this condition occurs, and
cannot be reset until the Exceed Condition has passed.
Also refer to Annunciator, Exceed Time, Latching Relay, Limit Controller, Limit Hysteresis
and Limit Setpoint.
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Glossary
- DIN Controllers & Indicators - Product Manual
Type: Limit Controller Definition
59305, Issue 5 – March 2005
Type: General Parameter
Type: Controller Parameter
Type: Controller Definition
Type: General Parameter
Type: Indicator Definition
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