70
Loop-Back Segments
A Loop-back segment goes back to a specified seg-
ment in the current profile. This action is repeated for
the required number of times (1 to 9999) before the
profile continues onwards. More than one Loop Seg-
ment can be used in a profile, but they cannot cross.
Figure 50. Loop-back Segments
x 500
Example: Runs segments 1 to 5, then
repeats segments 3 to 5 again 500 times,
before continuing on to segments 7
Loop
Segment
End
Loop-back target segment
Profile Running / Holding vs. Hold
Segments
Continue
Triggers
Hold Segments
End
Hold Start
Hold Stop
Run
Figure 51. Run/Hold & Hold Segments
A Hold condition during a segment maintains the cur-
rent profile setpoint value(s). Once the hold condition
is stopped the Ramp or Dwell continues. The user can
request that the profile holds, or it can be instigated
automatically.
Note:
A running segment will hold if the operator
or a digital input instructs it to. It can also hold due
to “auto-hold”, if one of the profile control loops is
disabled, if a cascade is set to “open” or if manual
control is selected.
A
Hold Segment is a pre-planned hold programmed
into the profile. It maintains the value of the previous
segment and the profile does not continue until a
Con-
tinue Trigger occurs. This can be via a key-press, se-
rial communications, a digital input signal or after wait-
ing until a pre-set time of day (time of day is available
with the recorder option only).
The Auto-Hold Feature
There are independent auto-hold settings for each seg-
ment of each loop controlled by the profile. When uti-
lized, auto-hold ensures that the profile and the actual
processes remain synchronized. If the process does
not closely match the setpoints (within the defined
Hold Bands), the profile will be held until it returns
within bounds. When Auto-Hold becomes active, the
profile status is shown as “Held”.
Note:
The segment time is increased by the time
that the process is out of bounds, extending the to-
tal profile run time.
Auto-hold can be configured to hold the profile if the
process goes beyond the hold band
Above the Set-
point only, Below the Setpoint only or it can be set to
Band (either side of the setpoint).
Note:
For two-loop profiles, either loop can cause
the profile to hold. The entire profile (i.e. both loops)
will be held if either process is outside of its auto-
hold band. It continues only when both loops are
back within their auto-hold bands.
Auto Hold Examples
Held if Auto-Hold set to Above Setpoint or Band
Dwell Segment
Setpoint
Hold Band
Process Variable
Held if Auto-Hold set to
Below Setpoint or Band
Figure 52. Auto-Hold on a Dwell Segment
During a Dwell, the dwell time is increased by the time
that the process is outside of the hold band in the se-
lected direction(s). This ensures the process was at the
desired level for the required amount of time.
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