SP-RAMP Logic Block Documentation

Overview

The SP_RAMP function block is designed to smoothly increase or decrease a set point (SP) from its current value to a target value over a predefined duration.
This block allows for bidirectional ramping — meaning it can both ramp up and ramp down.

By employing the SP_RAMP block, transitions are controlled, systematic, and safe, helping to avoid sudden fluctuations that could destabilize the process or stress equipment.

In the above picture we are showing the SP_RAMP block.

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Functional Description

• This block gradually adjusts the set point from Init_SP to the scaled Reqd_SP over the time defined by TM_PT_Span.
• It ensures a linear transition (either increment or decrement) within the defined cycle time.
• The output Finish is set to TRUE when the transition is complete.

In the above picture we are showing the example of connecting the pins.

In the above picture we are showing the example of using this block.

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Pins Information

Signal Name	Type	Description
Init_SP	REAL	Initial set point value from which the ramp will begin
Reqd_SP	REAL	Target set point value
Reqd_SP_Fctr	REAL	Factor applied to scale the required set point (e.g., for percentage adjustment)
In_Span	REAL	Input span limit (used to define allowable operating range)
TM_PT_Span	REAL	Base time span required for the set point to move from minimum to maximum
Cycle_Time	REAL	Execution cycle period of the block (time step for calculations)
Calc_SP	REAL	Intermediate calculated set point during ramping
Finish	BOOL	Status output: TRUE when ramping is complete, otherwise FALSE

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Operational Behavior

1. Initialization:
   The block reads Init_SP as the starting point and computes the target using Reqd_SP × Reqd_SP_Fctr.

2. Ramping:

   • The block gradually increases or decreases the set point.
   • The speed of ramping depends on the ratio of TM_PT_Span and Cycle_Time.
   • The Calc_SP output updates each cycle to reflect the current ramp position.

3. Completion:
   Once the calculated set point reaches the scaled target value, the block sets Finish = TRUE.

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Example Use Case

For example, in a flow control application, the operator might need to increase flow from 20% to 80% over 10 minutes.
Instead of jumping directly, the SP_RAMP block will gradually adjust the set point within the defined TM_PT_Span, ensuring smooth and stable process changes.

Similarly, in a shutdown sequence, the same block can gradually decrease the set point to zero, avoiding abrupt changes.

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Best Practices

• Set TM_PT_Span according to system dynamics — too short may cause oscillations, too long may delay response.
• Use Reqd_SP_Fctr = 1.0 if scaling is not required.
• Ensure Cycle_Time is correctly configured to match task execution cycles.
• Always check Finish before initiating dependent process steps.
• Suitable for PID transitions, gradual valve openings, pump startups/shutdowns, and flow/temperature adjustments.

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The SP_RAMP block provides a flexible, safe, and structured method for implementing both set point ramp-ups and ramp-downs, ensuring stability and reliability in automated processes.