This branch of engineering deals with designing, installing, managing equipments that are used to monitor and control machines in a production or manufacturing area.
Instrumentation engineers are responsible for integrating the sensors with the recorders, transmitters, displays or control systems. They are responsible for designing, testing and maintenance of control systems.
This branch actually stems from electrical and electronic engineering. It is a multi disciplinary stream and covers many subjects like electrical, chemical, electronics, computer engineering etc. Instrumentation engineers basically fix snags in devices or systems attached to big machinery. Instrumentation engineers work in power plants, chemical plants, manufacturing facilities, oil refineries, steel industry, drug manufacturing, and hardware companies.
Instruments are used to measure many parameters like pressure, temperature, level, flow, density, voltage, frequency, current weight, etc. Automobile industry and aircrafts use complex instruments and the simplest example of an instrumentation system one can see in a mechanical thermostat installed at homes.