Allen-Bradley LOGIX 5000 Reference Manual page 124

Chapter 1 Process Control Instructions
124
Ramping
The ramp cycle ramps Out from the previous segment's SoakValue to the current
segment's SoakValue. The time in which the ramp is traversed is defined by the
RampValue parameters.
Ramping is positive if Out < target SoakValue of the current segment. If the ramp
equation calculates a new Out which exceeds the target SoakValue, the Out is set
to the target SoakValue.
Ramping is negative if Out > the target SoakValue of the current segment. If the
ramp equation calculates a new Out which is less than the target SoakValue, the
Out is set to the target SoakValue.
Each segment has a ramp value. You have the option of programming the ramp in
units of time or rate. All segments must be programmed in the same units. The
following table describes the ramping options:
Parameter Description
Time-based ramping TimeRate is set to true for time-based ramping (in minutes)
The rate of change for the current segment is calculated and either added or subtracted to Out
until Out reaches the current segment's soak value. In the following equation, DeltaT is the
elapsed time in minutes since the instruction last executed.
Where RampStart is the value of Out at the start of the Current Segment.
Rate-based ramping TimeRate is cleared to false for rate-based ramping (in units/minute)
The programmed rate of change is either added or subtracted to Out until Out reaches the current
segment's soak value. In the following equation, DeltaT is the elapsed time in minutes since the
instruction last executed.
Guaranteed Ramping
Set the input GuarRamp to true to enable guaranteed ramping. When enabled, the
instruction monitors the difference between Out and PV. If the difference is
outside of the programmed RampDeadband, the output is left unchanged until
the difference between PV and Out are within the deadband. The output
GuarRampOn is set to true whenever Out is held due to guaranteed ramping
being in effect.
Rockwell Automation Publication 1756-RM006K-EN-P - November 2018