Answer Posted / ranjith
In Mahesh's answer, it says 'Nodes are I/O communication protocols' this part is wrong.
In a typical DCS architecture from top you have got,
0. MES/SAP/
1. Operator station
2. Runtime/Database/Historian/Batch/Gateway & Engineering Servers
3. Controller
4. IO nodes
5. Marshalling Panel
6. ...(I'll stop here)
The IOs are generally not clustered with the Controllers, IOs will be in a different panel communicating with the controller in various communication protocols(exceptions are there).
There will be a slave module communicating to the master(Controller) and also communicating to the IOs connected to its Backplane/Bus of the slave. This slave module and the IOs are collectively called as 'Node'.
There will be multiple nodes due to segregation of IOs(Plant/unit/Process part) or to distribute the slave module's load (different manufacturer has different IO density specified or may be limitation of protocol).
Now imagine wiring the whole bunch of field signal cables to your control room...!
An alternative is to take a communication cable from 'Main control Room/Center' to 'Remote/Sub station' may be kilometers apart and enjoy limited wiring.
Total number of nodes are limited by the communication protocols itself. (Payload, Noise, Cycle Time ...)
Further reading:
Industrial Communication Protocols /Fieldbus
| Is This Answer Correct ? | 5 Yes | 0 No |
Post New Answer View All Answers
what should he know if he is an assitent engineer instrumentation in cement industries of experience of 10 - 15 year.
What are different types of cable?
What is three element drum level control system why its better than single element?
when the instrument tapping on pipe line is located below and transmitter is located above the tapping point for liquid service transmitter, what should we do, is there any additional drain valve is required??
Somebody can explain me about >Critical Loops, calibrations, ESD critical Loop checks, Logic Diagram / Cause & Effect checks for ESD loops,
What is instrumentation control?
why any measurement made interms of pressure is more accurate ? to be more precise most of the flow velocity is made interms of pressure and it is accurate. what is the reason behind pressure measurement being accurate ?
What is instrumentation measurement?
which type of zones used for boiler? & why ?
What is three element in drum level?
Can anybody tell me how to select the size of earthing cable for DCS & PLC system.Please tell me any relevant answer here or mail it to me.
full process of gas turbin?
Why plc require in analog input 4-20amp & 0-10 volt?
What is instrumentation instrumentation engineering?
How to work temperature gauge?
