Producing steel products which meet the needs of customers requires not only smelting, refining, casting and working but also a number of related techniques. Important among these are techniques for analyzing composition, and for measuring and controlling the processes involved. As an example of advances in analytical techniques related to steel, the accurate determination of elements in real time has been made possible by instrumental analysis. With continuing progress in the production of high-purity steel, techniques to analyze the micro elements present in concentrations at the ppm level or less have become increasingly important. Measuring techniques involve monitoring chemistry, temperature, pressure, and dimensions with sensors, and processing the sensor signals in real time. Elimination of noise, and computation, data transmission, and recording in memory can easily be achieved as a result of progress in the digitization of signals. As the next step, advances in the technique called sensor-fusion are desired to make it possible to gather high-level information which is unobtainable from one sensor alone, but is available by combining the data provided by multiple sensors. Control techniques are indispensable to obtain consistent quality in mass production. Control involves changing the present state to achieve the desired state by carrying out appropriate operations. The system by which automatic control is conducted consists of the process to be controlled, the control system, and the sensing system, as shown in the figure. The values obtained for process variables which have been recognized and measured by sensing are then compared with the target values. Differences are converted by the control system into the variables and transmitted to the operation terminal which controls the specific process on the basis of variables, the result again being monitored by the sensing system. This cycle is conducted repeatedly. The area of science and engineering used to design the most effective control system is called control engineering, and aims at applying the optimum control system and sensing system following a complete analysis of the process being controlled. Control theory is widely applied to centrally control the utilities used in steel works, as well as the whole process ranging from treating the raw materials to producing the final products.