Hi,

I'm using S7-1200 to control sterilization process in a lab.

I have IO-link master with a water level sensor mounted to control pump. To sterilize the water, I need to calculate the chemical concentration in which derived from the water level at time T. This calculation gives me a targeted water level for the pump to achieve

Further, I need to save/store this water level at time T so that I can use it as a boundary for comparator instruction. I.E water level process value >= targeted/calculated water level for sterilization.

But, I only have one water level sensor, thus when the pump start pumping the water level reference for calculating the targeted water level will change, thus my targeted water level will change and the pump will never stop. 

Can anyone show me alternative or solution to store process value on a specific timeframe?

Hello inder22,

as I understand it is intended to store data one at a time that is retrievable and not to be overwritten during the process. There is an FAQ with an example program that can help you, at least in part.

With the blocks from this library, you can save up to 12 different return values one after the other in a data block with the S7-1200/S7-1500.This program can of course be expanded further.

In STEP 7 (TIA Portal) how do you buffer the return values of FBs and FCs one after the other in a DB?
https://support.industry.siemens.com/cs/ww/en/view/43511056

With best regards
Cicero