Converting the input ( analog voltage - 0 to 10V /current - 4–20 mA) into the understandable engineering values as per industry standard ( analog voltage - 0 to 10V /current - 4–20 mA) is called “ SCALING ” .
The Input instrument which is producing analog values( for eg. 0–10V) is give to Analog Input Module. This module converts that analog values into counts/raw value (i.e) 0 to 32768.
Whenever the input instrument produces 0V our PLC reads 0.
Similarly , Input Instrument 5V = PLC reads 16384.
Input Instrument 10V = PLC reads 32768.
So using this raw value , we can scale our PLC to convert the Input to Output as engineering values as per industry standard so that we can control the output device.