Hands-On Industrial Internet of Things

Disadvantages of the PLC

PLCs are at the first level of the automation pyramid. This means that using them to get data means working very close to the hardware, with a low level of abstraction. This brings the following problems:

• The PLCs, and the PLCs that act as data concentrators, manage, either directly or indirectly, several thousand input and output signals plus their internal data, calculations, and statuses generated by their control logic. In the context of the I-IoT, all of these are tags, some of which come from physical instruments and others from internal calculation and intermediate logic steps. These often appear unstructured, or structured in a very basic way. They are rarely linked to a comprehensive data model, even though ...