Dear Sir! I faced a problem with total flow calculation. I have never had any

expirience with flow calculation before.

Here is a system we have: There is a s7-1200 controller which has a connection

with  Schenck weighing system via Profibus. The weighing system acts as a slave.

It has a total flow counter tag, which I am able to access via controller.

Also there is a computer (operator's station) which is connected to s7-1200 via ethernet. Wincc Advanced v.13 is installed on the computer. (tag logging was bought as well).

There are three different materials will go through one weighing system. And operator has to pick which one is going to be transported (by choosing one on the screen). When he picked one, only that

materials would be taken into account, others two wouldn't be changed.

I consider the following options: Create a tag in the controller. And each 10 seconds

controller would find the difference between initial total flow and total flow after

10 seconds. This difference would be put in the tag I created. Then I would put this tag in archive.

1)Is it the right option?

2) How to create a report in excel and make an sql queries?

3)How to treat an event when counter is reset to zero?

4) What to do  if computer is switched off?

I need to create an excel report, that will  automatically write  a flow calculation value every shift. It should be written in one file. Every day it should move to another cell in excell

Hi Rashid,

Do you have the option to reset the total flow via a command from the PLC? If so, you could zero the counter every time the material is changed, then simply read the total at the end of the batch.

If that's not an option then I would go about it in basically the same way you suggest:

...each 10 seconds

controller would find the difference between initial total flow and total flow after

10 seconds. This difference would be put in the tag I created. Then I would put this tag in archive

Do you need to keep a record of the total as it accumulates or are you only interested in the total flow at the end of the batch? If the latter then there would be no need to archive every 10 seconds - just log the value when the batch is complete. We use a similar method to calculate pump flow totals.

This FAQ entry gives details on using SQL with WinCC Advanced:
How do you access an SQL database in WinCC Runtime Advanced using a script?

If it is possible that the counter can be reset to zero by an external process (reset button, overflow, etc.) then your code should include a check to make sure the current total value > start value. If the check fails then you can decide what action to take e.g. raise an alarm, discard the value...

If the material doesn't change while the computer is switched off it won't cause a problem - the data you need is still stored in the weighing system and PLC.

If the material changes while the computer is turned off then you will lose the data for that batch. An alternative would be to store the totals for the last few batches in the PLC. You could do this using an array or look into datalogging using the PLC itself:
Sample program: S7-1200 and DATA LOG

Hope this is some help,
Regards,

Craig.