Instrumentation is the art of measuring the value of some plant parameter or physical amount (pressure, flow, level or temperature) to name a few and supplying a signal that is proportional to the slow parameter.
The output signals are standard signals and can then be handled by other tools to deliver indications, alarms or automatic control. There are a number of standard signal;s. hHowever, those most public in a plant are the 4-20 mA electronic signals and the 20-100 kPa pneumatic signals.
Instrumentation engineers are commonly responsible and looking for integrating the sensors with recorders, transmitters, and displays or control systems, and are responsible for calibration, testing and the important purpose of the system.