In process industries normally different manufacturing process requires maintaining constant temperature or temperature variation allowed to 0.5% or low. Such temperature control of chemicals/ process ingredients is critical precision temperature control is not possible using conventional ON/ OFF controllers.. Secondly, present market trend is changing fast and requires investment in equipment, which has large degree of flexibility, and production sequence can be manipulated change with ease, such that batch production becomes flexible and programmable. Particularly in chemical industry temperature at which reaction are required to be performed are very critical, and need to be controlled under all dynamic disturbance conditions. Such diverse requirement is feasible for a system only with PID controller that permits fast response with minimum over shoot and error. As per the flexible process requirement of manufacturing industry, the complete process must be programmable, Hence these requires use of microprocessor/ micro-computer/ micro-controller as basic element of the design. For implementation of the above process requirement, the problem for the research is proposed here.