Instrumentation is defined as the art and science of measurement and control of the process variables within a production or manufacturing area.
The process variables used in industries are Level, Pressure, Temperature, Humidity, Flow, pH, Force, Speed etc. Control engineering or control systems engineering is the engineering discipline that applies control theory to design systems with desired behaviors.
Control engineers are responsible for the research, design, development and control devices/systems, typically in manufacturing facilities and plants.
The practice uses sensors to measure the output performance of the device being controlled. Those measurements can be used to give feedback to the input actuators that can make corrections toward desired performance.
When a device is designed to perform without the need of human inputs for correction it is called automatic control (such as cruise control for regulating a car’s speed).
Multi-disciplinary in nature, control systems engineering activities focus on implementation of control systems mainly derived by mathematical modeling of systems of a diverse range.