Hello, 

I am designing a control of pH in a tank for which I am using a PID_Compact. It offers several measure types (pressure, voltage, lenght, etc) but no pH.

I have two options:

1) Either choose another unit (pressure) and set limits to 0-14.

2) Choose percentage (%). The problem with generic percentage is that it is more difficult to work with 0-100 than real meassures like 0-14.

¿Does this affect my PID (tuning, performance, ..) or it is not really important?

Hi!

I use a 1214C PLC

Hi Railito,

the selection of physical quantity and unit in PID_Compact, PID_3Step and PID_Temp has only influence on the GUI of the TIA Portal engineering system (display of unit in configuration, commissioning and traces).

It has no effect on the controller behavior or the tuning.

Regards

Thank you very much, that's what I suposed.

Cheers