Types of Instruments
Pressure, Temperature, Flow, Level and analytical.
Flow, Pressure, Temperature and Level.
Process control consists of three instrumentation elements. Measurement, evaluation, and final control. The final control element is probably the most important because it exerts a direct influence on the process. Final control devices contain the essential pieces of equipment to convert the control signal (generated by a process controller) into the action needed to correctly control the process.
Control valve is a final control device. A control valve is simply a variable orifice that is used to regulate the flow of a process fluid according to the requirements of the process.