A PLC Logic Controller is essentially a digital computer that controls mechanical processes. This means that it can receive and send many instructions in order for a machine to carry out its functionality. They integrate with machinery such as those used in the automobile industry, lights or even to operate a fully functional amusement park.
Their uses are varied but are mainly concentrated in the mechanical production sectors. They are used because of the way they are built. They can withstand high levels of electrical noise interference, different degrees of temperature ranges and are virtually impregnable to impact and vibrations.
It is for this reason that they make use of magnetic storage often termed non volatile memory. This means that a PLC unit backs up its information similar to how a flashdrive used for personal computers will back up its memory. This form of magnetic memory storage is termed long term persistent memory.
The benefits of this are, is that in case the unit has a power outage, it can continue to store the information already in the system. These units also make use of a battery pack to act as a secondary back up power source. Non volatile memory specifically implies the use of secondary or long term persistent storage.
Another functionality of this type of input and output systems is that their operation occurs in hard real time. This means that operations are carried out almost instantaneously or in a very short amount of time. If this is not achieved it has an adverse effect on the functionality of the mechanical device it is operating.
Logically, this effect is detrimental to the processes it is carrying out. For example on the assembly line of an automobile industry, millions of instructions are relayed to various mechanical systems and instruments to carry out work. Should an instruction from this unit not relay that message within a required time frame, it will throw all the other processes out of synchronization.
For these very reasons the units are built with durability in mind. They also make use of non volatile memory. This type of memory is comparable to magnetic tape storage. An example of this type of memory storage can be likened to a memory stick or flashdrive used on personal computers.
A PLC logic controller can be found in most factories making use of production lines. Their durability and reliance upon is essential in carrying out the tasks it is intended for.