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What the MASTER-SLAVE system is like?

The Master Slave system means connecting more controllers when one apparatus is controlling (master emits required value) and the other apparatuses are subordinated- slave apparatuses (they receive the required value). It is possible for subordinated controllers to shift the required value by desired difference (parameter dIF1 at service function level). The connection of controllers is shown in the following figure, the controllers are galvanically separated from each other..

As long as for this type of control only two apparatuses (master a slave) are involved it implies that only one communication bus RS232 is sufficient. If more than two apparatuses are used (as many as 32) it means that it is necessary to apply communication through the EIA485 communication bus. It is not necessary to use as master only the parent controller but PLC industrial system or PC computer can also be applied. In communicating with the computer through the EIA485 line it is necessary for the PC to be equipped with the EIA485/RS232 converter. Then the computer makes monitoring and data collection from all the apparatuses involved possible.

What is the Cascade control?
It is suitable to use the cascade control for the systems with big transfer delay i.e. for the systems where the response to contact making of actuating element is too large (e.g. for muffle furnaces, ). The principle of the cascade control is the division of transmission delay into two parts, which results in control quality improvement. The controller of the external loop measures the temperature inside the furnace and emits the required power of the inner loop controller. The controller of the inner loop recalculates the required power to the required value that is the temperature controlled in the vicinity of the heater.