Troubleshooting Multi-loop Control Systems (ATS02)

This comprehensive INVOLVEĀ® interactive multimedia training program was produced in association with the Instrument Society of America (ISA).

This three lesson program trains participants in efficient methods for finding the cause of a problem in a system and correcting it.


This lesson is designed for participants familiar with instruments and their functions within a control loop and how they are represented on process control diagrams. An understanding of a systematic approach to troubleshooting single loop control systems is also required.


This lesson discusses the application of the steps for applying the systematic approach to troubleshooting multi-loop control systems. Emphasis is placed on isolating possible causes to the appropriate loop of a multi-loop control system. The lesson applies the basic troubleshooting procedure to ratio, cascade, and feedforward systems.


Apply the systematic approach to troubleshooting malfunctioning multi-loop control systems. Read and interpret a control diagram of a multi-loop system, identifying the process variable controlled and the input and output devices for each loop. Verify that a performance problem exists by gathering information as necessary from such sources as the operator, diagrams, trend graphs, historical data, and system performance. Locate and identify the possible causes of a performance problem in the quickest, most efficient way possible. Divide a multi loop system into logical divisions to isolate possible causes. Once the problem has been located, identify and carry out or recommend appropriate corrective action. Verify that corrective action has been taken by consulting resources and take or recommend appropriate follow-up to minimize the potential for recurrence. Apply a systematic troubleshooting approach to its proper conclusion in ratio and cascade control as well as feedforward/feedback systems.