Flow totalizer

todell · Sep 11, 2010

Hello All,

I need to display total gallons pumped on a remote display. i am using a flow meter with 4-20 output scaled in GPM. The analog value is stored in D0760 of my Idec Pentra PLC.

I divided D0760 by 60 to get the gallons per second and stored the value to D0000. A one second timer updates D0000 every second.

How do I add up the updated D0000 values to get the total gallons?

longshanks · Sep 11, 2010

todell, I am not familiar with your PLC, but the way I've done something similiar is to use a rung just before you read the new value to move the "old" value into a "buffer" register, such as D0765, and then add the "buffer" register, D0765, to a "totaalizing" register, say D0770. In this way, D0770 would update each time you get a new value and give you the total just before the read. The register numbers, of course, are arbritaary and up to you.

todell · Sep 11, 2010

Can someone provide actual ladder logic of this. Every way I have tried this it does not totalize. It only provides a value which does not update.

sthompson · Sep 11, 2010

todell said:
Can someone provide actual ladder logic of this. Every way I have tried this it does not totalize. It only provides a value which does not update.

Which exact PLC are you using. Make and full model number please.

Stu....

todell · Sep 11, 2010

Idec Microsmart Pentra FC5A-D16RS1

JERA · Sep 11, 2010

todell said:
Can someone provide actual ladder logic of this. Every way I have tried this it does not totalize. It only provides a value which does not update.

Maybe something in this style.
1 second pulse moves analog value to D1000, which added to the total value. D1000 is then reset and ready for the next pulse / analog value.
So one time per second the total value is updated by adding the new analog value to the total register.

Hope this will give you an idea for solve this.

UPS: The move for reset the total value, have also to be a (D) type.

todell · Sep 12, 2010

Thanks Jera, The add function changing D1010 after adding was the key.

Stationmaster · Sep 12, 2010

That PLC has a 1 sec clock pulse built in that may shave a little off the ladder.

Stationmaster

Flow totalizer

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