analog input/output

I am a plc rokie, I can only understand simple ladder logic and I would be grateful to learn more from you guys. Anyone can explain to me anything about analog input/output and how the data being manipulated in the program? Any help would be appreciated.

james patricio said:

Anyone can explain to me anything

Click to expand...

what exactly would you like to know?


in general, you basically wire voltage source, let's say ultrasonic sensor, (for example 0-10V), or current source (for example 4-20mA) to the PLC's analog input and each scan (or right from the any part of the program in some cases in some PLC brands) you have a variable(or memory area) with the value proportional to the voltage/current level.

and the same story with analog outputs, you just write the value to the variable and get a proportional level of the voltage/current from the analog output...

the most important difference from the digital I/O is that you dont just have 1-bit signal, but do have something like 12-bit value

For example, if you use Step7 to program, The analog input is a word and designated PIWxxx ;xxx=word address

The analog output is PQWxxx
The word addresses is defined in the hardware configuration.
usually, the analog value inside the PLC is in a range (example: from 0 to 27648) which corresponds the physical value (example: 4-20mA), Where 0->4mA and 27648->4mA
You have to scale your output or input with the value inside the PLC.
Example:
you have a level sensor from 0 to 100m
You then need to scale the range (0 - 27648) with the physical value (0 - 100m)
Then you use scissors multiplication to get the value as follows:

Physical -> PLC
0m -> 0
100m -> 27648
Ym -> X

then Y=(X * 100)/27648
Where: X is the input from PIWxxx
Y is the distance in meters

Thanks a lot mr girevik.
I am sorry, i posted a very vague question that you found it hard how and where to start answering. Anyway, at least I learned from you guy the basic principle of analog input/output. If it's ok with you, can you send me a sample configuration of analog input/output (ex. temperature or pressure controller) and its plc program (a ladder diagram)using mitsubishi plc. Thank you very much guy.

Thanks Mr. Amazingahmed.
I now got a clearer picture on how to use analog signals. I guess its just a matter of studying more and putting it into practice. Thanks guy, you help me a lot.

i have no any experience with Mitsubishi PLC..

try http://forums.mrplc.com/index.php?dlcategory=16

I think the best way to learn is to read the manual and try it.
At least work for me...

absolutely agree