Honeywell VRX180 user manual Soak segment, Guaranteed Soak, Hysteresis

Setpoint Profiler

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.

Guaranteed Soak Limit Check	Guaranteed Soak (Segment “n”) = ON
Profile Segment “n”	AND
	Guaranteed Soak (Profile) = ON
	Guaranteed Soak High Limit
Hysteresis
	Setpoint (VALUE of profile)
Hysteresis	Process Variable (PV#1)
	Guaranteed Soak Low Limit

Returned below limit and hysteresis - Profile resumes RUN

Setpoint deviation still within hysteresis - still on HOLD

Excessive deviation - Profile changes to HOLD State

Figure 5-7 Guaranteed Soak and Hysteresis

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