Glossary · Control theory and process control
Split-range control
Also known as: Split-range loop
German: Split-Range-Regelung
In process control, split-range control is a structure in which the output of one controller is divided into ranges that drive two or more actuators in sequence, for example a heating valve over one half of the output range and a cooling valve over the other.
- Control theory
- Process industry
In one sentence
Split-range control drives two or more actuators in sequence from one controller output, such as heating and cooling valves.
Example
A reactor temperature controller opens the cooling water valve from 0 to 50 percent output and the steam valve from 50 to 100 percent.
How it applies
- Engineering: Split-range control extends the operating range or switches between heating and cooling. The gains of the two actuators often differ, so a single tuning may be a compromise; overlap or gaps between the ranges need deliberate design.
- Commissioning: Check the transition point closely. Valves that don't close tightly or have different characteristics cause cycling around the split.
- Documentation: Show the split as a diagram: controller output on the x-axis, actuator positions on the y-axis. Operators and service staff understand the logic far faster from the diagram than from text.
Split-range vs. selective control
In split-range control, one controller drives several actuators. In Selective control, several controllers compete for one actuator. Both can be combined in complex loops.