44
…3 PROFILES
3.2.2 Guaranteed Ramp/Soak
If the process variable deviates from the set point by more than the hysteresis value, the program status is set to
'
HOLd' and Guaranteed ramp/soak is applied automatically. Each program has two associated hysteresis values:
HYS.r – applied to ramping segments, and
HYS.S – applied to soak segments.
The hysteresis value can be set within the limits '0' to '9999' where a setting of '0' implies that no deviation from the
set point value can be tolerated.
Hysteresis can be applied in one of four ways, with individual settings for each segment:
OFF – hysteresis not applied, ramp/soak not guaranteed.
HI – hysteresis applied above set point ( Holdback ('HOLd') set if PV > [SP + Hysteresis]).
LO – hysteresis applied below set point ( 'HOLd' set if PV < [SP – Hysteresis]).
HI.LO – hysteresis applied above and below set point
( '
HOLd' set if PV > [SP + Hysteresis] or PV < [SP – Hysteresis]).
Set
Point
Time (Hours or Minutes)
Process
Seg. 1 Seg. 2 Seg. 4 Seg. 5
End of Profile (revert
to Local Set Point or
repeat of profile)
Set Point (Eng. Units)
Adjustable Holdback Hysteresis
1. for Ramp segments
2. for Soak segments
Adjustable ramp rates
Skip Forward
Manual
Pause
Holdback Active
outside hysteresis
limits
Hysteresis applied Hi-Lo
(above and below the set point)
Hysteresis applied Hi
(above the set point)
Start
Seg. 3
Note. Ramp segments can have a different hysteresis to soak segments.
Fig 3.4 Typical 6-segment Ramp/Soak Profile
3.2.3 Power Recovery Function
The Power Recovery function allows pre-selection of the restart position within a ramp/soak profile when power is
restored after a failure.
With options
A, b or C, if power is restored before the Power Down Time expires, the ramp/soak profile continues
from the point at which power failed. If power is restored after the
Power Down Time has expired, the profile resumes
from one of the following user-selected points: start of the current program; start of the current segment or from the
profile position at the time of failure. In all three cases the controller restarts in
HOLD mode.
With option
d, the profile continues in run mode from the position on the profile that would have been reached had
the power failure not occurred.
To Next Page
Loading...
