Totalizer

[MajorFault]

Hey guys,

Looking for suggestions on how to program a totalizer in a ControlLogix5000. We have a scale under a conveyor belt thhat measures the amount of wood flakes going across it. 4-20 coming back to PLC is converted into a value representing lbs. I take a snapshot of this value every second to give a lbs/sec value and then convert that into lbs/hr.
What I need is a totlaizer that would represent the total weight of wood that passed over that scale in a 12 hour shift. Of course total pounds in an hour would work also. Values usually run 30,000 to 50,000lbs per hour. Converting to tons to keep the numbers lower is ok, I just need a total.
Have any of you tackled a similiar application?

Thanks for any help!
MajorFault

 

[Ken Moore]

If your version of RsLogix5000 supports function blocks, there is a totalizer function block available.

From the online help:

Description

This instruction typically totals the amount of a material added over time, based on a flow signal.
The TOT instruction supports:

§ Time base selectable as seconds, minutes, hours, or days.

§ You can specify a target value and up to two pre-target values. Pre-target values are typically used to switch to a slower feed rate. Digital flags announce the reaching of the target or pre-target*values.

§ A low flow input cutoff that you can use to eliminate negative totalization due to slight flowmeter calibration inaccuracies when the flow is shut off.

§ Operator or program capability to start/stop/reset.

§ A user defined reset value.

§ Trapezoidal-rule numerical integration to improve accuracy.

§ The internal totalization is done with double precision math to improve accuracy.

 

[demmons]

You could ADD the value of your lbs/sec snaphot to a file every time you get a new snapshot, then manipulate that file to represent tons.

 

[MajorFault]

Totalizer works great!!!
Thanks for the help!

 

[Ken Moore]

I guess you can use function blocks, glad it worked out for you.

 

[MajorFault]

Sorry, yes I used the function block as you suggested.
Works great, quick and easy to implement.
Saved me alot of time vs. ladder.

Thanks again.