PLC 101 (< pun) - I'm not hearing the magic words?...
EDIT: KingPresident - I was trying to compose a post below to guide our friend towards the answer here, more so than just giving it to them. You've now mentioned the magic words that were missing. But, I feel, you are still not quite correct in your understanding of the general terminology used with respect to PLC "Points", or you have over simplified them (more later).
I'll continue and finish the post as was intended...
Ryan,
Welcome to the Forum!
Dudge1981 said:
...Can anyone tell me what the on off point in plc is called ?...
...It was a question thst my friend got in a test, it ask what are the on off points in a plc are called ? . He said digital...
"Digital" would not quite be correct, in my opinion.
I won't give you the answer. I'll just attempt to guide you towards it. That way you, and your "friend", might learn to think about these things a bit more, rather than just having the answers given to you. That's how we best learn, is it not, after all?
The question is essentially asking this -
On / Off Points - What is another way of describing these "Points" for a PLC?
With respect to "Points" on a PLC, "On" and "Off" may describe the status that these type of "Points" may hold, but what is the best term to use for describing PLC "Points" in general?
Clue 1: For a PLC, "Digital" decribes the type of "Points" where the only status available is either "On" or "Off" - Example: a switch contact or an indicator lamp.
"Analog" describes the type of "Points" where the status available is not simply "On or "Off" but is a potentially dynamic value - Example: measuring or controlling temperature.
Clue 2: For all types of PLC "Points", how are the signals from the connected devices directed to and from the PLC "Points"? How do we best describe the sending and receiving of signals between the PLC and the connected devices?
While KingPresident has esentially given you this answer, it needs to go a step further...
KingPresident said:
...on off should be called IO.
KingPresident,
You are now missing a descriptive term before "IO". There are different types of "IO", as you have pointed out, but how do we best describe "IO" that may be either "On" or "Off"?
There are actually 2 common terms used to describe this type of "IO", and they both start with the same letter. Bonus point for getting both of them?
(No Gurus need apply, but of course may add their comments if they so wish).
EDIT: That was funny rdrast - it is a poorly worded question, if it has been relayed here correctly. So I do hope my interpretation of its meaning is at least in the ball park?
Regards,
George