What type of instrument system corrects changes using feedback from a process?

A closed-loop system is designed to automatically adjust a process by using feedback from the output to influence the input. This feedback mechanism allows the system to continuously monitor its performance and make necessary corrections to maintain desired levels of operation, such as temperature, pressure, or flow rates.

In such systems, sensors play a crucial role by measuring the actual output and comparing it with the desired setpoint. Any deviation from this setpoint triggers an adjustment mechanism, ensuring that the system operates within specified parameters. This dynamic relationship between output and input is essential for maintaining stability and achieving efficiency in various industrial processes.

The other options relate to systems that do not incorporate feedback in the same way. An open-loop system operates without corrective feedback, meaning it does not adjust based on the output. A feedback-free system, by definition, would lack the essential mechanism for adjustment based on output, and a sequential loop system may suggest a series of steps without continuous feedback correction. Thus, the closed-loop system is the correct answer as it embodies the essential characteristics of adaptive and self-correcting mechanisms in process control through feedback.