Answer / sachin patel

PLC is the Solid State device. Which is used in Discrete &
Sequential logic in which Timer, Counter, Relay in the form
of Software Called the PLC.
It is two type- 1- Compact or Non modular plc.
2- Modular plc.
* In compact PLC I/O are fixed (Allenbradilly,
Seimeance,Mitshubishi plc )
* In Modular PLC I/O are Increase. (SLC- Sequential logic
controller).

DCS is the Distributed Control system. It is advance of the
PLC. It is used in Big Industry. In DCS I/O is nearly 1 lakh.

HMI- It is a Human Machine Interface.It is used for field
instrument control.

Answer / ghanshyam khatri

plc is programmable logic control ,plc is used in small
application,it is works on small program which is created
in computer then send to plc.plc have memory to store this
programme and then perform.
hmi is human machine interface,hmi is used for smaller
appliction then plc.
dcs stand for distributed control system this is used for
big plants(for larger amount of i/o)

main diffrence in plc n dcs is
1.in dcs we can change programme during it is working,this
is not possible in plc.
2.in dcs trend and history is available.

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