After having learnt the technology and process control of the Sinter Plant I studied the features, used additional modules, as well as development environment of OMRON CJ2H PLC.
After having understood the system, I prepared the parts of the PLC program that are specified for me as task, i.e. the reading, correction, digital filtering of analogous signals, as well as the calculation of the measured quantities, and the temperature and pressure correction of those.
The managing of temperature values is also included in the reading of analogous signals. I programmed this program part in the form of ladder logic, adding the orders put into the ladder. The cycle time can be controlled well on such a low level, as it is exactly known how many elementary orders are performed, but the developed program is not transparent, so program parts have to be disassembled later again to correct the error occurring during operation. I wrote further parts with the help of function blocks in order to improve transparency.
The programming of function blocks makes it possible to use a structured language of higher level, therefore the implementation of selected algorithms became significantly simpler. It could practically be performed after the conversion of variables by giving the proper formula.
After having written the PLC program I created a panel in SCADA and HMI system that the values provided by the PLC can be easily found in by modules and channels. The operator detects immediately if a line is broken and the technician can read which the channel to be checked is.
The new program could be operated by the time the Sinter Plant was stopped in November. The various program parts were successfully put together. The PLC was placed into the instrument box of the Sinter Plant and has been operating since then.