Instrumentation and control Engineer  is a very specialized branch Instrumentation and control engineering (ICE) is a branch of engineering that studies the measurement and control of process variables, and the design and implementation of systems that incorporate them Process variables include Level ,  Pressure, temperature, humidity, Control , Flow, pH, force , Density , Safety , Different types of sensor, analyzer Automation incluide Programmable Logic controller (PLC) , DCS ( Distributed control system), SCADA (Supervisory control and data acquisition), PID Controller 

IP rating means is also known as Ingress Protection or International Protection ratings which is defined to the international standard of EN 60529 (British BS EN 60529:1992, European IEC 60509:1989). These standards are frequently used to define the levels of sealing effectiveness of electrical enclosures against intrusion from foreign bodies such as dirt and water.  The rating consists of the letters IP followed by 2 digits, the first digit stands for the level of protection that the enclosure provides against solid bodies, the second digit describes the degree of protection of the equipment inside the enclosure against water and 3 digits is optional (Pressure)

The Hazardous Area Classification, now simply called as Area Classification, is standardized so that any industry can relate to it and classify their Fire hazard. It must be remembered at all times that the Area classification is a risk based approach and is not a certainty, since many permutations & combinations of properties (e.g. climate changes, ventilation etc.) can alter the degree of fire hazard.  Manufacturers provide standardized solutions and devices to control or totally mitigate the Fire hazard based on such classification

This standard establishes a uniform means of depicting and identifying instruments or devices and their inherent functions, instrumentation systems and functions, and application software functions used for measurement, monitoring, and control, by presenting a designation system that includes identification schemes and graphic symbols. Various  graphic symbols used Instrumentation schematic diagrams of the instruments, devices, and functions required for monitoring and control loops., functional diagrams of instruments, loops, and application software functions,  Binary logic diagrams,  Ladder diagrams of electrical circuits.

Transmitter is the device used to transmit data from a sensor over the two-wire current loop. There can be only one Transmitter output in any current loop. It acts like a variable resistor with respect to its input signal and is the key to the 4-20mA signal transmission system. The transmitter converts the real world signal, such as flow, temperature, speed, position, level , humidity, pressure , motion or signal etc., into the control signal necessary to regulate the pressure of current in the current loop. The level of loop current is adjusted by the transmitter to be proportional to the actual sensor input signal.