What are the difference between Fixed, Modular, Rack PLCs ?

Fixed PLC:

The fixed plc containd each and every component in a single unit that contains CPU,input/outputs sections and powersupply the number of inputs and outputs cannot be expanded.

 

Modular PLC:

Slot tgether to build up a system. modules like CPU,input/output module.

it's main advantage is that the number of inputs and outputs can be  expanded .they are directly fixed to back panel and they are usually arranged in rack or rail mounted inside a large cabinet for protection and security

 

Rack PLC:

this is similar to mudular plc's they are arranged in rows on a rack inside cabinets.they do not plug into each other but plug into a standard communication slot in the rack .all the slots are connected by standard network or bus so that they all communicate with each other.This is expandable system..

 

Fixed: It is a Compact PLC in which no modification can be done whether it is AI,AO or DI,DO. Modular: In this PLC you can expand the I/Os as per your convenience... Rack: In this PLC u can add the I/O modules by mounting on the rack which are of4,7,11 rack types available.