calculation of no of input/outputs

HI!

What is the diagram form which we can calculate no and type of inputs/outputs of PLC called?
And how it is calculated?

Awaiting the response.

It's called 'addition'...

There's no 'formula' for the number of inputs and outputs. You just make a list (called an "I/O List") and just count 'em. When you get to ten on your fingers (assuming you still have all of 'em), you can use your toes to keep track of the 'tens' place...

If you want to do some 'calculation', you can multiply the number of I/O by some percentage to allow for expansion. And no, I don't mean thermal expansion...

beerchug

-Eric

bonkhead

Thanks a lot Eric but I had learned that before i was sent to school.

Mindwell i asked about the Diagram and not the Formula
I think u didn't understand or u r unaware about it as i am.

I was asked by the interviewer at a small system integrator and also at M.N.C. the following "question".

For deciding the configuration Of automation system u r given a digram hopefully called "P & N " diagram from which u can calculate no and type of I/O?

What is that diagram or say the document called and hoew do u calculate from it.

Eric is right,

Thats the one thing I always done here, because it was the requirements of the PLC manufacturer. First they are going to ask how many input/outputs you want. To know the number of inputs, you have to know how many interlocks, switches, buttons, etc. you need. Second, you have to know how many motors you have to run, or other things need to run. Then prepare what you called I/O list. From this, the manufacturer will know how many CPU will be required from the system you submitted.

Like here, mostly we are requesting each area with its own CPU, because you still considered the scan time. Example, in our roughing Area..one set of plc, Intermediate Area, another set, Finishing Area another set again. For Auxilliaries load such pumps, it is another set of plc again.

Sorry but I agree with Eric. Do you know what I/O is? Regards Alan

achalconst said:

I was asked by the interviewer at a small system integrator and also at M.N.C. the following "question".

For deciding the configuration Of automation system u r given a digram hopefully called "P & N " diagram from which u can calculate no and type of I/O?

What is that diagram or say the document called and hoew do u calculate from it.

Click to expand...

Why didn't you ask it that way in the first place?

The closest I can come is the term "specification". A document or diagram describing system function.

If my customer was nice enough to diagram exactly what they wanted (we are lucky if they know that!), it would make my job a lot easier.

Are you looking at a specific industry? It seems only in a very large company would you hope to get a document like that.

I think the P & N diagram he is refering to might be a P &ID. I use this drawing in conjunction with job specifications to figure I/O count.

Well, then, what does P&ID mean?

Gotta love those Acronyms

Piping and Instrumentation Diagram

Ahh.. process stuff. I figured that it was specific to something.

P&ID Diagrams

A P&ID drawing is exactly what achalconst is looking for. They will look very similar to an electrical blueprint and should contain a legend as to the symbols. All devices used in the particular process will be drawn on this drawing. With each of these devices will be symbols (sometimes the symbol and the device are a combined symbol) denoting what I/O and type of I/O is required (if any). I will try to locate the website where I found some standard symbols and post it. It takes a little getting used to, if you have had no experience with this, but it is not that difficult.

P&N Diagram

achalconst
The P&N diagram you are referring to is a "Purpose & Need" diagram, it serves the same purpose as the P&ID.
Just about all companies have P&ID drawings in some form, that represent the schematic map of their process plants which needs to be maintained. The P&ID should have all the components shown to develop an I/O list. One thing to keep in mind is that all engineers do not draw detailed P&IDs and others over complicate or clutter up the drawing with unnecessary items, so it would serve you well to know the process as well as possible.
None the less a P&N\P&ID is a good starting point for your I/O list.

I hope this answers your question.
Roger

93IT1, for a long time P & I D has been used as the acronym for Process and Instrumentation Diagrams - at least that's the way the ISA (Instrumentation Society of America) defines it.