Reading analog I/Os with profibus, Freelance
I have a problem with the analog I/Os with my moduls on AC700F on profibus.
I have a signal (4-20 mA) in an input. But with de profibus, the data in Control Builer is an integer.
So, when I have 0 mA (open circuit), I have -32768 for my integer.
With 4 mA (0%), I have 0
With 8 mA (25%), I have 6900
With 12 mA (50%), I have 13800
With 16 mA (75%), I have 20700
With 20 mA (100%), I have 27650.
My question is... what is this number ? I can understand that my number could be between -32768 and 32768 (2 bytes), with 0-32768 for the 4-20 mA part. But 27650 is a strange number...
Nevertheless, there is a linearity between 4 et 20 mA. I can easily make a scaling. (Cf picture). But I whant to understand...
And sorry for my bad english.
PS : I have CBF 2013.
In Profibus the values are often provided as integers, and scaling depends on the module type and selected mode (compare 4-20mA and 0-20mA). You have to look up the scaling in the module's manual.
If you use S700 modules as Direct I/O, the function blocks provide converted values, but if you use them via Profibus, you have to do conversion yourself. There are templates to support configuration of S700 modules in the export directory: S700_Template_US.hwm