Honeywell VRX180 - Manual (Page 196)

Setpoint Profiler
Video Recorder – User Manual 182
Soak segment
All soak segments have a beginning VALUE and a TIME during which that value is maintained. This is
true regardless of the ramp type used.
Guaranteed Soak
Guaranteed soak will Hold the profile value if either PV to the profile (typically a Control Loop’s PV)
deviates specified amounts above or below the profiler output. See Figure 5-7. For a guaranteed soak
to occur, the following conditions must be met:
1. The GUAR SOAK #1 and GUAR SOAK #2 prompts for the segment (ramps and soaks) must be
enabled (set to ON),
and
2. The GUARANTEED SOAK discrete input to the profile must be enabled (level high).
If either of these are disabled, a guaranteed soak cannot occur, even with excessive deviation between
profile and PV.
Hysteresis
This parameter specifies the amount the deviation between profile and PV must be reduced before the
profile resumes running after a guaranteed soak. See Figure 5-7.
After a guaranteed soak the profile will resume running when the deviation has decreased by this
amount.
The following examples assume GUARANTEED SOAK is ON(1), and the example segment’s GUAR
SOAK #1 is ON(1).
Example #1
Assume PV #1 is 20 units above the profile output, GUAR SOAK HI LIM is 15, HYSTERESIS is 5. The
profile will Hold because the deviation high limit is exceeded. The profile will resume running when the
PV #1 is 10 (15-5) units or less above the profile output.
Example #2
Assume PV #1 is 20 units below the profile output, GUAR SOAK LO LIM is 15, HYSTERESIS is 5. The
profile will Hold because the deviation low limit is exceeded. The profile will resume running when the
PV #1 is 10 (15-5) units or less below the profile output.
Setpoint (VALUE of profile)
Guaranteed Soak High Limit
Guaranteed Soak Low Limit
Hysteresis
Hysteresis
Process Variable (PV#1)
Profile Segment “n”
Excessive deviation - Profile changes to HOLD State
Returned below limit and hysteresis - Profile resumes RUN
Guaranteed Soak Limit Check
Guaranteed Soak (Segment “n”) = ON
AND
Guaranteed Soak (Profile) = ON
Setpoint deviation still within hysteresis - still on HOLD
Figure 5-7 Guaranteed Soak and Hysteresis